Although, the merit system has no perfect modality for disbursement and I've seen many users delivering the 50 merits at once to other users. Just like franky1, he enjoys doing that at once. This could be at anyone's discretion since it's flexible, yet, I love it if it is being used wisely and distributed effectively instead of wasting it on just a post while other more meaningful posts are being neglected.
I don't know if there is any method to send merit but for sending merit it must be a good quality post. There is no rule to award merit without merit. To send merit, it must be a good quality post only then merit can be given. I've also seen good quality posts get 50 or more merit majors at once. The posts I saw that sent 50 merits or more were very good quality merit posts. Here the post in which he gave merit was not given in full merit post. It is a misuse of merit.
About your concern, the suspicion here is that the user who sent the merit was a dead horse that just arose again for the purpose of sending the merit. This could indeed be concerning but may not be as we thought of it at times. Regardless of how it is, it is certainly an abuse of merit sharing of the forum, especially when the post merited is not worth any merit, not to mention handing it a whole 50 merits at once. That's gross.
The matter of sending talent is accepted but not so much is accepted in any way. It makes no sense for him to send so many merits to this post. These should be noted. Misuse of merit is that they must be warned against this, not everyone can send merit like this.
That is it, when there are no further rules to back fair usage but entire freedom for the usage, there will be abuse (directly or indirectly), and this abuse is mostly not provable since there are many freedoms to it. No matter how people could defend this, I still believe that it is unless the post is intriguing, so respectable and above all adds huge value to the forum itself, it's only then that it could be worth the 50 merits at a go. But I see some posts that are worth less than 2 merits attracting 50 merits at times. I mean very short posts with no serious worth of appreciation.
I don't care about what users do to defend this anymore, people are sending merits based on sentiment, that's a fact and sentiment doesn't make it perfect. I'm also done thinking about the merits system of a thing, it's not worth it and it is what it is.
We should all live by it (fair or not) and try to be of quality with our posts mostly for the sake of the forum and not for the merit itself. If merits come, fine, and if it doesn't come, fine.
The most important thing is for your username to continue speaking of who you are, something which the merit system itself can't deny you.