Recently people have been having problems with the way some punctuation characters are being displayed on the forum.
It seems that if you copy something from Microsoft Word that includes certain characters, such as ?smart quotes?, it can come out looking weird.
Contrary to suspicions, I don't think this is caused by a recent update to the software underlying the forum, because there has been no recent update. It's a few months since the last upgrade I applied to the SMF (Simple Machines Forum) package. What might have changed is still a mystery to me.
However, the problem may be able to be solved by converting the forum database to the UTF8 character code. I'll try that out over the next couple of days.