I expected to be able to use unicode characters like √ in realms description and name.
But what actually happened was that the unicode characters turned into ? when submitted.
You can reproduce this by typing a √ in the realm name.
You may think that "why would anyone want to use a √ in their name?", however, some character used for language like ਊ doesn't work either.
Confirmed in Realms version 1.7.39 for Minecraft 1.8.8