Don't know if that counts as bug:
Create a custom profile field which allows a large number of characters.
It flows out of the MCP box (screenshot 1) and - worse - out of the "box" on viewtopic (screenshot 2). The latter case could be prevented by adding overflow: hidden; to .postprofile.
For the first one, removing autowidth from the class attribute seems to help.
(Side note: in ACP, it does not overflow; there's no autowidth either but: max-width: 100%