Thanks to a comment by @LargeHardonCollider@lemmy.world , I checked and saw that 'Federation debugging' mode was enabled. I had enabled that when the server just started (less than 3 weeks ago) and I had an issue with federation.
I thought I had switched that off again, but apparently not. This mode causes the federation to be done in the foreground, so your 'Post' or 'Comment' action will wait for that to finish...
This solves the most annoying issue, and makes the site way more useable. There are many other issues, but we'll get there.
Could you have a look at https://lemmy.world/u/limbodev? I tried setting it up last night and got the spinner and no confirmation email. I can see the account was created, but get the spinner if I try to log on to it.
I've been trying to create a few accounts on different servers today (not for spam, for dev work :-) and it seems to me that this is happening primarily when I try to create accounts from Safari. If I fire up Chrome everything runs correctly, so this may be a UI issue rather than backend. I don't know if that helps or hinders...
If you are able to reset or delete limbodev, that would be appreciated!