jibberish, rhubarb, whatever, etc.

314 above to this 315

spam, spam, glorious spam. 316

321? What happened to 317, 318, 319, 320? Posted & deleted but still counted. Don't tell Gizmo or he'll be up to 10k in no time.

I think this was normal behaviour back in Classic as well.
Posts deleted are still counted unless you manually hack the database.

correct

Yes, otherwise it'll nuke posts, which would piss off users... let alone it'd require the db to have to be updated, for every user, when mass deleting threads, for every post... which just woudln't be logical...