>>6516127bbcode on 4chan (or in general?) works weirdly, if you want to spoiler something inside a word (like the classic spoiler "rrat" in "narrative"), you have to do na<spoiler><spoiler></spoiler>rrat<spoiler></spoiler></spoiler>ive but with [ and ] instead of < and >. I have no idea why. A basic regex wouldn't have that problem, so I don't understand what's the issue