The Arch wiki may have some ideas for you - tl;dr is that GDM uses a global dconf db over in /etc/ and this might be the root of your problem (these configs might not get cleaned up with a --purge?) I’m a LightDM user so best I can do to help: https://wiki.archlinux.org/title/GDM#dconf_configuration

The other data shows that posts and comments are going up linearly (a little suspicious but OK), but I wonder how the modlog affects the data (meaning how is it captured and when). I made one comment to a honest post yesterday (hosted on a remote instance), which then the post was deleted by admins like so:

Removed Post Any app for call recording ? reason: Rule 2: Please use [email protected] for support questions.

So my comment shows in my history but cannot actually be accessed; was this comment counted? was that post counted? Was I counted as an active user yesterday if that was the only activity I did all day? Was the one person who upvoted my comment before the thread was deleted counted?

Lies, damn lies and statistics. :)