Sorry to hear you've been stricken with the dreaded "Word Wrap Bug". I've experienced it myself a couple of times for brief periods--maybe a week or two--before that right-hand margin just snapped back all on its own, the cure just as mysterious as the cause.
Despite "Tooseevee's" misplaced notion of my knowledge of the Forum system as being "intimate", the fact is we're not even barely acquainted. Despite my very grand-sounding and relatively recently-acquired "Global Moderator" title, this just means I'll occasonally pull on my size 11½ cowboy boots for those communal roach stomps we have from time to time when spammer scum pop up here like farts in an elevator/lift to peddle their scummy wares.
Rest assured though, as our REAL Admin "Dantheman's" already explained, they're aware of the recurrent problem, but a solution remains elusive. For now I can only reassure you that it usually just "fixes itself" somehow.
And just as a treat for Tooseevee, here's Nanci Griffith belting out "Once in a Very Blue Moon"...And yes that IS Lyle Lovett back there doing harmonies:
https://youtu.be/GS7vW3rPnNk