Gajim sends messages with thread element, and Smack sends delivery receipts without it. Gajim ignores it and marks message as not delivered.
I found discussion with exactly same problem here: https://trac.gajim.org/ticket/5128 They suggested correctly handle XEP-0201 and keep thread element. Shoud Smack do the same?
Smack’s behavior is correct. There is no need to include in a message containing only a . I also fail to see where xep201 requires this. Nor what Asterix tries to explain in https://trac.gajim.org/ticket/5128#comment:15
As it appears now, I believe this to be a Gajim bug.