Same as another board I have and that board doesn't have the problem. They are on completely seperate servers though. Could it be a server configuration issue?
It could be many things, varying from the characterset used in the database, MySQL versus MySQLi, instaled PHP modules like mbstring/iconv. Very hard to tell from a screenshot.
I just checked and the characterset of the database is the same. And this problem only came up a few months ago, so it has to be hack related. I guess I can just disable them all and re-enable one at a time to narrow it down. I thought it was because of the post edit history hack since it started around that time but I removed it and still no change. I'll get it figured out though.