What happened here?

[Chocolate Misu]

I've never seen this happen before. It's half way down on the page here Let's Give Some Reputation Points!

[arthurgolden]

I see it, too.

Who knows? Sometimes a single page of a thread will all be in bold, or will all be italics, for no particular reason. Sometimes posts wander out of their boxes, like you showed above. As for why...

[Chocolate Misu]

I've seen CC's shiner page be almost entirely italic and never changes, and I remember some thread way back sometime was half comic font. I've never seen the post out of the box before though...

[Jessie]

It's because there's too many spoilers.

And it's gone.

[Chocolate Misu]

Ah thanks Jessie I'll have to remember that spoilers break posts

[CC]

I had a feeling that was caused by Bsnowman and his DeVry-honed Spoiler Pyramid!