Multiple deletions don't quite work

The logic is like this: When a message is collapsed then the message and its children are deleted (recursively). When a message is expanded then only the message itself is affected by the deletion.

This goes for many actions including marking as read/unread, flagging, tagging messages.

Note that the left-right arrow keys can be used to collapse/expand.

Let me know if this does not resolve your problem.

Apologies, but perhaps I didn't explain this correctly.

What happens is I select a few threads, not just one, all in the closed state, and
click delete. When I do that, often, but not always, only one message is deleted
and the selection is then cleared. If I again select the same threads (minus the one
that actually did get deleted) and click delete a second time, often that will
cause all the threads and their messages to be deleted.

Let me know if this still doesn't seem clear and I'll wait until one my my
mailboxes gets a few threads of automated mail (it's usually lots of commit
mail from the FreeBSD source code control mailing lists) and I'll figure out
how to capture it in a small movie file and upload it here.

OK, here it is as a captured movie. Hopefully this will give you enough info.