If you want to have posts merged in the first hour for everyone except for your spammers who are most likely to double post, and you put them in an extra spammer group with a 24 hours time restriction, that won't work because your spammers will still be in the registered group with a 1 hour time limit.
Yes, there is a way, if you have a verified group and don't put the spammers in it (or remove them from it if they are suspected)
In priority order
Registered gets long time to double-post merge (say 24 hours)
Spammers get same time (24 hours)
Verified group gets less time (4 hours)
Mod group gets less time than verified (1 hour)
Admin exempt
You can't do this with your addon if someone is part of Reg, Ver, Mod, Admin
You would have to re-work it such that:
Registered is a base with 0 merge time
unverified user is a secondary group with a high merge time (24 hrs), spammers might never get out of this group
promotion to a verified group could happen, but you can't remove someone from a group as part of a usergroup promotion
If someone is a mod, you have to remove them from the verified group then back in the permissions they would get to the Mod group, which defeats the purpose of using secondary usergroups to grant successive permissions
Admin exempt per permission works because they can be in all groups and it doesn't matter - so that feature is very nice actually. But you are forced to do that because if an Admin is not a Mod then they can't see the mod log due to the way XF works in that regard
So as you can see, not doing it the WMTech way creates a lot more problems than it solves, you have to re-work your entire philosophy about how to structure usergroups just so you can use this addon the way that it should logically work. Unless you only use it to post-merge one or maybe 2 usergroups, and exempt most others. But if you incorporated this addon into an existing usergroup framework with 30 usergroups and successive permissions for less time to merge as you progress up the "ladder" with users being added to groups but not removed from lower groups, this addon won't work at all for that...
Does that make sense?
The reason I'm bringing this up is that this was a really big deal with the older version of the XF1 addon that WMTech took over - it was originally structured exactly the way you've structured this one (without the exemption permission) and everyone complained. So I'm trying to help spare you that whole argument again. The only way to make this work in a manner that is instantly and easily integratable with an existing usergroup structure/philosophy is the way they did it.
