Thanks for the report.
TL;DR summary - I will get this fixed tonight.
I looked into this issue on Friday and found that it’s a problem caused by a plugin (the abbreviations tooltip plugin), which is incompatible with the latest core Discourse code.
I was hoping the abbreviations plugin would be fixed over the weekend (taking in a fix is easy and doesn’t cause downtime to SE23.life). Unfortunately it hasn’t been fixed yet, yet, so I think the plugin should be removed from our forum.
Removing a plugin means about 8 mins of downtime and so I’ll need to do this late at night to avoid disrupting the site. I’ll aim to get it done tonight.