Sending or receiving merits is not proof of anything. Do you have actual proof or at least a reasonable suspicion that something is not "normal" here, e.g. merit being sold, or the accounts being alts of each other?

I'm sure you can find greater amounts of merits spent in a shorter period of time for posts that (to you) may seem not deserving. Merit sources and other merit senders are encouraged to try to send out as many merits as possible and put the halved merits back into circulation. In fact it says right there on the merit page: "There is no point in hoarding sMerit; keeping it yourself does not benefit you".

MichaelX is a 4 year old user who's still a Newbie. He's not a spammer, so there's no damage to the forum by Meriting him. There's also nothing gained by MichaelX.
I sometimes send a lot of Merit to one user, and I don't think that's Merit abuse.

I guess it's only a Merit source thing to have to search for good posts. I'm happy when I can "unload" a bunch of sMerit, and I'm happy to see new users who aren't spammers. They're the future of this forum (and Bitcoin)!