Just editing out a "Hello" is a waste of an edit and reviewer time. It does not make the post better, it does not make the issue any clearer. All it does it waste review time.
Using your example's revision log, I'd say:
- #6 was a waste. It should have been rejected.
- #5 Was good. It fixed many other things and made the post better.
- #3 and #4 were a bit washy but didn't require multiple people to approve them.
- #2 again made the post better. It does edit out the "Thank you" at the end but it does more at the same time.
So in cases like Revision #6, reject them. I think there is a "petty edit" reason in there but otherwise just explain that it doesn't actually make the post any better.
If you see an edit like Rev #6 on a post like the original —where the post still needs a lot of work doing to it— reject it but improve it at the same time. By all means cut out the small-talk but make sure everything else is polished up at the same time.
But don't conflate small edits with petty edits. A small edit could completely change the meaning of something (or fix it). Use your discretion and look for overall value when reviewing suggested edits.