When a message is deleted, Thunderbird automatically selects another message from the list and opens it in the preview panel. That's super annoying because it will eventually mark the other message as read even though I wasn't intending to read it now. It might also fetch remote images (if enabled) or have other consequences.
There was an extension for this long ago, but since most extensions broke with a previous Thunderbird update, there's currently no way to do it. For this and other reasons (removed several features) I'm still using the old version 60. This is really a trivial fix and there shouldn't be an extension needed for it, that will eventually break again like all extensions did at some point.
PS: The combination of terms "delete" and "deselect" is impossible to search on this platform. Only the term "delete" is considered by search.