(#fj7dppq) @movq@www.uninformativ.de Thanks for the summary!

So, what would happen if there is no original message anymore in the feed and you encounter an “edit” subject? Since you cannot verify that the feed contained it in the first place, would you obey it?

Some feed could just make a client update something from a different feed. In the cache, the client would need to store in a flag that this message was updated, so that when it later encounters the message from the real feed, it has a chance of reverting that bogus edit. Hmm. The devil is in the detail.

It’s much easier with a delete subject. When it finds the message in its cache and the feeds match, remove it. Otherwise, just ignore it.