Feeds: Successful fetch but no posted article for domain

I have a bit of a strange situation to report.

I use the feeds integration in multiple rooms with multiple domains and subdomains. And it seems that all feeds from `shivering-isles.com` and subdomains of it e.g. `git.shivering-isles.com` seem to be fetched successfully (according to the integration UI), but never posted to the any room where I set them up.

It seems to happen across multiple backend software, multiple rooms, multiple feeds. The only thing in common is that they run on my domain. (example feeds: `https://shivering-isles.com/feed.xml` or `https://git.shivering-isles.com/shivering-isles/infrastructure-gitops/-/tags?format=atom`)

Since the bot reports successful fetches and I also see them in the webserver logs, it is not a connectivity problem either. I'm not sure what else I can do on my end to make things working again except of running an own bot at some point.

Other feeds e.g. from other websites that I setup seem to work perfectly fine, so I don't think it's related to my account either.

Start by reproducing the feed integration with shivering-isles.com and git.shivering-isles.com feeds, comparing them with a feed from another website. Trace the successful-fetch path through to room posting and determine why these feeds produce no article; done means affected feeds are posted while existing working feeds remain functional.

Written by the indexing model from the issue text.