One of the obvious drawbacks to giving a lot of merit that's supposed to be for overall good posting is that it'll get questioned, as it did in this case. That post linked to in the OP didn't deserve 50 merits IMO, but I see where TMAN was coming from.
I agree with you on this point. TMAN is a good source, not only because he helped me but also what he did for the other good posters in the community. Being a source is kind of official task and somehow it puts pressure to finish works as sources.
If we look positively on what TMAN has done, we might agree with him on this approach, only because his lack of time and his past right decisions to dump merits on very good posters. I have not observed TMAN but occassionally when I saw him gave away 20 - 30 - 50 merits to the others, all of them deserve those merit dumps.
The latest one, that resulted in the drama is TMAN dumped merits on the bad OP, and it is a root cause. No one at their first glance, spending time to look at post history of OP, they simply and only look at the bad OP's contents and the 50-merit transaction.
Gettting merit dumps are always much happy, I know. I remembered the first time I got 14 merits dumped by actmyname in 2018, it's my sweet memory. Who have not yet experienced such dumps are jealous with the others (please don't deny that). But to be honest, with or without such merit dumps (from TMAN or the others), I am going to rank up, obviously.
In a summary, I suggest that if sources are lack of time to scan the forum and find good posts to dump merits; they should choose at least a good poster, scan post history of that one, then dump merits (10, 20, 50, it depends) on one of good posts of that one. It will not cause any drama, I believe.
Drama causes some users withdrawn their roles as sources (at least Vod). Have you ever imagined TMAN's source-withdrawal will be good for the forum? Being a source is a silent work, without payment and you guys ask for too much, IMO.