Decide on special characters to accept/reject

[dreeves]

My Latest Arguments Against Slashes In Particular

1. We may want slashes to have special meaning so we shouldn't allow them willy-nilly in the meantime and make a (bigger) backwards compatibility mess.
2. Bots and humans try dropping stuff after slashes, like going up a directory. This would be a feature in the case of @chrisbutler's folders idea but is bad in the status quo.
3. A related problem is that it's not obvious that URLs like alice.commits.to/reply_to_bob/by/5pm and alice.commits.to/reply_to_bob/by/4pm are treated as entirely distinct. Change those to alice.commits.to/reply_to_bob_by_5pm and alice.commits.to/reply_to_bob_by_4pm and it's more clear that the system won't try to do any magic to treat those as referring to the same underlying promise.

[dreeves]

In fact, I believe that if we did want to accept slashes we'd need to implement a solution like slash blindness: https://github.com/commitsto/commits.to/wiki#option-2-slash-blindness