There are many work-arounds for certain limitations. Sometimes we fix them, and sometimes we say "meh". If the restriction prevents a couple of "Ok." comments, it has fulfilled its purpose.
Back when I didn't work for Stack Exchange (or Stack Overflow, as it was called), I reported something similar, and found Jeff Atwood's reply boring. But he really was right. When you allow users to post stuff, there's always going to be someone who uses the magic of Unicode to do smart and/or funny stuff.
As long as it's something that can be looked over (like one in a million comments apparently getting around the character limit), that's fine. If it happens too much, we'll prevent it, but it'll always be a game of cat and mouse – sooner or later someone finds something else.
And if someone starts doing actually harmful stuff – well, then the answer is "don't do that". It's abuse. Abuse isn't tolerated and will be handled.