I haven't put a lot of effort in researching this so I don't know which ones, but here are at least four: ~, /, \, #
In my code I had a log message like this:
I wanted to remove it and tried searching for ~, which didn't show any hits. In the end I did find it using other methods, but the main point is that the search didn't work for that character.
(Why did I search for it instead of just clicking it in the log window to go to it in the IDE? Because it was in a b4xlib, so I can't click it.)