Phil Boswell:
Something like a tilde surrounded by double square
brackets would probably
be appropriate:
[[~]]
Please, no cryptic symbols like that. The point of a toolbar is to make
it intuitive to format wikitext. A newbie neither knows what double
square brackets mean nor what "~" could stand for. The blue, underlined
"Ab" works perfectly well. Sure, it's Latin characters, but they are
internationally recognizable.
Best,
Erik