It's not merit abuse, the only logical reason is that the user was a senior member when the merit system was introduced, so he got airdropped 250 Merits but then later on, the user decided to massively delete his past posts probably because they were shitty posts and the number of activity also went down until it reached member level
How do you know they deleted their posts and got downgraded as opposed to them having the potential activity to be a senior member and that thus awarded them the merit...
If you look at BPIP, there is no record of received merit by the user... it means that's just airdropped merit.
EDITGuess you already figured that out.