The reason this is "invalid" instead of "won't fix" is because it's not a bug; it's intended by the design. Essentially, when I made that map I figured the quirk of having him fly through the glass wasn't bad enough to matter and allowed me to quickly make the level changes I needed to make, so I just ignored the quirky behavior.
As an example, another "by design" quirky behavior is the way our game behaves when you leave the water. Springs and other such features let you go flying, and that clearly makes no sense by any rational physics engine. This bug in the classics is reproduced in our game, but it's not a bug in our game because we did it on purpose by design to replicate the classics.
Since this is bug reports, and bugs are unintended quirks in the game, this isn't a bug and the report is invalid. That doesn't mean it shouldn't be fixed; it just means it's not a bug.