(If you don't want to read this giant post, then my main point is below the dotted line (or you could just go to the TL;DR section at the bottom). Also, when I say "Max Running Speed, I mean the top capped speed you can get by holding forward on un-sloped terrain.)
I doubt this post will help anyone, but I wanted to put my own thoughts out there about the situation.
I've read over this whole thread, and, strictly gameplay wise, the argument seems to be that "if STjr removes Sonic's Thok, something will be lost" or if the Thok is gone, Sonic loses an aspect of his gameplay that the other's do not have. I've thought the same, but wasn't sure exactly why that was. So I played through SRB2 3 times now to figure out what exactly do people appreciate about the Thok?
Now I wouldn't call myself a professional speedrunner, but I like to try and go as fast as possible through the levels when I play them. But the biggest problem with the Thok is it's unwieldiness to newbies and how it gives the player free speed on a silver platter, so I will not so much as ignore those aspects of the move, but focused my efforts on what other attributes the Thok may have. Also, other's have said how Sonic doesn't seem to have his own way of movement that gives him access to parts of the level that others cannot reach, like how Tails and Knuckles do, and that he shouldn't because that's how the classic games functioned.
But SRB2 does not follow a lot of the things that classic Sonic games do, and that's completely fine. Although people do get annoyed (myself included) about how a lot of recent Sonic fangames (SRB2 included, but I am not saying this to call SRB2 a 'new' game) have been replicating the classic game's design philosophy and therefore make the fangames feel "samey", but I realize that they do so because the classics have phenomenal design fundamentals (when the levels and characters are designed around it) which give them their distinct feel that makes those games stand apart from other platformers; the mastery of your movement along with the geometry of the levels to bring yourself to the goal in the quickest time possible, in the most basic sense, which is why many felt that the 2d games until Mania felt subpar compared to the classics.
SRB2 is first and foremost a Sonic fangame, which is why so many beginners had trouble controlling Sonic when first playing the games. But this is a problem concerning the core engine of SRB2, which is why the developers (STjr) have been retooling the game. The main problem however is Sonic, or more-so his ability, the Thok. In a game where using your abilities to interact with the environment to increase your momentum is encouraged, having your main playable character give you "free speed on a silver platter" (the speed of the Thok is almost twice the speed of your max running speed!), it undermines the fundamentals of your game, which is only made worse by the fact that your platformer's level design punishes the player if they abuse its' unwieldiness by slamming you into a wall, spikes or to your death via a bottomless pit (not to say these punishments are a bad thing, it's only to prove the point that the power dynamic compared to the other characters' abilities is quite unbalanced). Especially so for the fact that almost all beginners will choose Sonic.
But to me and probably a lot of other players, calling the Thok simply "free speed" feels wrong. It feel like to me personally, there would be something lost if the Thok was removed without a clear answer of what Sonic's replacement ability will be, which STjr seems to be bothered by. Like maybe there is something more to it that should be further looked into.
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Now I finally get to the part where I discuss and answer the question I asked at the beginning of what as a discussion on one ability that soon became an essay on the fundamental issues of SRB2, or more specifically Sonic in it, so I guess we looped back to talking about the Thok.
This is pretty much the TL;DR section of my reply.
Besides just giving you a boost of speed, the Thok's most apparent ability is that it propels the player directly forward from where the camera is facing. The most obvious benefit from this is the fact that, for example, you want to make a turn while
keeping your momentum, you could use the Thok and make a quick turn.
The Thok's second usage is with the environment, where if you use the Thok into an upwards slope, you gain a good amount of upwards momentum, which is most useful when you want to clear a gap or cross quickly onto a higher platform while, yet again, keeping or even increasing your momentum. You can do the same thing on Badniks or destructible objects, giving the player an easier access to a Badnik bounce.
Both of these are incredibly useful to obtain and preserve momentum, a core (or
the core) aspect of classic Sonic games.
And interestingly, another move from another Sonic game does this: the Drop Dash from Sonic Mania.
To use the Drop Dash, you jump in the air and hold the jump button down to charge a midair Spindash, which gets released when you touch the ground, giving you an increase in speed. If you are moving faster midair, or hold the charge for longer, the amount of speed gained increases. And, just like rolling, when you use the move on a downwards slope, it is more effective, giving you more speed.
Sounds like the same move, right? Almost makes me wonder why STjr haven't just--you know--replaced the Thok with the Drop Dash?
But if you were paying attention, these moves actually work differently. Firstly, the Thok, in its most basic sense is instantaneous and increases your speed almost to twice your max running speed in SRB2, while the Drop Dash, in its most basic sense, has to be held until you touch the ground, and increases your speed to your max running speed, unless charged for a certain amount of time. Also, the Thok is a midair move, where if you use it onto an
upwards slope, it increases your upwards, or vertical momentum, while if you use the Drop Dash on a
downwards slope, it increases your forwards, or horizontal momentum.
Perhaps, if both moves were added to Sonic's moveset and made to behave more similarly, in the fact that both only give the player their max running speed (unless they are moving faster than so), it will make Sonic a character that dominates horizontal movement, unlike Tails or Knuckles who dominate vertical movement and traversal respectively. This will only be a better change, when in future updates of SRB2, maps are designed with more verticality in mind to compliment the momentum physics-based engine the game will have, where Sonic won't be able to easily access vertical pathways but stronger in horizontal ones. Implementation could also be taken in the other direction, as while Sonic can't as easily gain vertical momentum like Tails or Knuckles, his superior control over his own momentum (and I repeat--
momentum, not speed), and will allow him to control himself in the air better after launching himself off of a slope to land on a farther or higher platform.
The real
TL;DR: In the end, I feel like focusing Sonic's moveset more on
momentum, not speed will make him a better pick for beginner players, as his moveset will not be as useful as Tails or Knuckles unless you learn to use your environment to gain speed, which is the fundamental aspect of classic Sonic games. With my idea of giving Sonic either a modified Thok & Drop Dash or some new ability that combines the two's main attributes I mentioned, Sonic having a (primarily) momentum-based move makes the most sense in a momentum-based series.
Giving beginners this OP ability (compared to the other characters) with no skill ceiling will leave them confused, especially in the future where SRB2 will focus more on gathering and keeping your momentum in a level.
(Did I get everything right?)