Hey \href{https://mathchan.org/test/thread/39}{I noticed} links posted here get "cloaked" through the \icode{exit?u=ID} endpoint. This is bad.

Link-shorteners make link-rot so much worse. When a shortening service dies, all links it resolved are lost forever too. By acting as a middleman, shorteners add another point of possible failure in the chain: \url{https://www.economist.com/international/2012/10/13/cut-short}

If mathchan dies, links in threads people may have backed up or archive die too. Perhaps this is OK or intended in sites designated for ephemeral discussion, but I get the impression your site is for discussion of pretty serious topics. Think about people, X years, who want to reference dead threads from here and do so through a 3rd party like \href{https://web.archive.org/web/20220111171441/https://mathchan.org/meta/thread/520}{the wayback machine}. Or people today who simply want to read your site offline and want know where links lead to at least.
Don't mess with links.