Is there a way to automatically “unbump” topics (meaning: not show them at the top of the list any more) when a moderator removed or split into its own topic the newest post that bumped the topic in the first place?
So many users abuse old topics with slightly related topics, so moderators regularily do this, but the (now unchanged) old topic still gets listed for these changes (and also adds the avatar of the moderator for added credibility).
There is no way now to do this but it sound like a reasonable feature request.
It’s possible that if you delete the redirection stub it will unbump … not 100% sure.
There’s definitely a fair bit of work we need to do here to improve the splitting and merging experience… @eviltrout I’d like to spend a day or two on this in the very near future.
If the redirection stub is the last post, deleting it will cause the topic to never appear fully “read” - it will always be black instead of grey on /latest. Same with deleting any other small post: pin, close, archive, etc.
Another bug that needs fixing 
We should add this to the 2.4 release list, we’ve put this off for too long. I’ve done so.
Note that you can now manually “reset bump date” after splitting. It moves the topic back down in topic lists. Furthermore, the issue with moderator shown as the most recent poster is solved if you delete the “xxx split this topic xx ago” line.