Recently there's been a problem where certain symbols do not appear in posts, but are replaced by spaces. See line 16 in the post
here, for example.
Edit: I'm not sure how it's triggered, exactly, since it seems to work OK in this post.
Plus symbols: +
Ampersand symbols: &
(But
not in preview, where both symbols fail to render, as well as everything after the ampersand.)
If you quote or edit the post, they remain gone.
Obviously this is very bad when posting code in particular.
In
this post it's also suggested that under certain circumstances it can "break" the post, though I'm not sure exactly what's meant by that (maybe the preview problem?).