Don't "fix" nonexistent profile picture URLs.
Fix forum-specific CSS when a custom posts-view.css exists.

Previously the custom posts-view.css would be used even after selecting a
forum-specific theme. Now the custom posts-view.css only takes effect when we'd
normally use the stock posts-view.css.
Fix ongoing edits becoming replies when appending quoted posts.

Previously, if you edited a post, then cancelled out of the reply screen, then
quoted some other post, it would look like you had simply appended the quoted
post to your edit. In reality, your edit just got transformed into a new post.
That no longer happens.
Helpfully space out quotes when appending them to ongoing replies.
Long-tap videos to open them in Safari.

Some YouTube videos refuse to be embedded, but might work elsewhere.
Formatting.