dunno if its the case here, but remember that bold, underline, colors etc also count as signs - the server doesnt see it as a control code, but just as signs aswell, so for example a topic like "14This is my 15 Topic " is actual 27 character, though it apears to be 16 character to your eye.
to test it:
//echo -a Visible length: $len($strip(14This is my 15 Topic ))
//echo -a Actual length: $len(14This is my 15 Topic )
