Is it actually possible to read 4 posts in 4 different sections within less than 2 minutes?
Maybe. But it's not necessary to Merit a post right after you're done reading. I usually open Merit-links in a new tab so I can continue reading without interruption, and Merit 4 posts within a second later on:
July 25, 2021, 07:42:51 PM: 4 to valentine wheeler for How to grow into a hero and legendary member?
July 25, 2021, 07:42:51 PM: 4 to DdmrDdmr for Re: How to grow into a hero and legendary member?
July 25, 2021, 07:42:51 PM: 4 to valentine wheeler for Re: WHICH COUNTRIES COULD FOLLOW EL SALVADOR BY MAKING BITCOIN LEGAL TENDER?
July 25, 2021, 07:42:51 PM: 4 to Ratimov for Brief History of Bitcoin Adoption
It looks like he just decided that he wants to give merits and clicked the last posts of them and sent merits.
As a Merit source, I do that too sometimes. Once I stumble upon a user who I think deserves more Merit, I check several of his posts. Nothing wrong with that:
if they have decent posts, by all means, give them the 250 or 500 merit that they need to rank-up.