Add a bunch of underscores to a post, and the entire page's word wrap is disabled for as long as those underscores are there. For threads with a lot of words, this could be a huge issue. Or just for mobile users.

aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa

It doesn't seem to just be underscores - any word that's too long to wrap expands it. It's also possible that this is only an issue in post previews, as those work differently (hence this post to test it). It would be neat if we had a public "testing" subforum for stuff like this.

EDIT: yeah, it seems like aside from the single word that's too long, everything else wraps properly in actual posts.

overflow-wrap: break-word; on .middle-post.post-body

Edit:

Added to userstyles

Not gonna lie, that kind of scrolling is a little funny to me. Also, the scrollbar that's added is in an awkward position -- it overlaps the copyright notice by a little bit.

We could use this to "preview" the first few lines of code to people, and they'd have to scroll to see the rest.

More generally, there's no reason to prevent breaking anywhere so I've applied break-word styling globally.