Yes I can see those being favorites for obfuscation - in general work its likely better to avoid the use of overly meaningful characters. I'd include sigils at the top of that list, then other things that are likely to confuse (like the pound character). I waver between the various bracketed characters - curly braces, square braces, chevrons and in last place parentheses. Which one I actually use is predicated on what the content of the expression is and whether it conflicts with my delimiters.