Not a big deal but making a post with a spoiler sometimes adds another show/hide button to all the spoilers on that page after hitting the post reply button. I'm gonna try to pin down exactly how to reproduce it with a few subsequent posts.
I'm on Chrome 27.0.1453.116 on OS X.6.
Ok, think I've got it pinned down. Either:
1) Making a reply with a spoiler, previewing it, then posting
2) Making an edit of a post with a spoiler (regardless of whether the spoiler was there before the edit or not)
... adds a second show/hide button to every spoiler in every other post on the page in question, excluding the edited/new post and the OP (if applicable).