As the moderator who made the edit, I can explain my reasoning. Please pardon the length of the post as I am re-posting the comment thread. I agree with you that this was an iffy edit; I wrestled with it myself.
Wouldn't a more appropriate response have been a comment to that effect and potentially a down-vote?
Absolutely...(...) if it weren't for the comment thread which did affect my decision-making process (I neither down voted the answer, commented, nor upvoted any of the comments, just to be clear.)
There was an argument in the comment thread beneath the answer in which the user strongly defended use of the Myers-Briggs personality test, which was brought up in the original answer.
The original answer (part deleted in the answer is in italics):
I wouldn't discourage following musical talent. Although he may never be good, it may be a good release when he needs to think. Thomas Jefferson was not amazing but often played the violin when he needed to think things through.
We tend to gravitate toward things at which our personalities excel. You could even have him take a personality test and look at other things he may enjoy.
The comment thread then consisted of the following:
- X: Is there any evidence that personality tests do anything except make money for personality testers?
- Answerer: You don't have to pay take a personality test. Just go to 16personalities.com. People have been studying personality types send Plato and Socrates. Each came up with different personality types the value different things in different ways. There is a lot of science behind personality types. David Keirsey describes how personality types determine how we evaluate and view our self worth, our self-esteem, and our self image. David jerseys book comes as a paperback and you can buy them supercheap secondhand. – hazmat 2 days ago
- X: Sorry, but Myers-Briggs is total bunk.
- Answerer: Hey grew the article that we are not strictly one type. It is a spectrum and it is important to understand that. It does not mean that we do not fit into categories or that we do not value things differently. I also agree that the coaching industry that is been built up around this is total garbage. But let's not throw out everything because of some scammers trying to take advantage of people. I have personally found that personalities make a big difference in what type of job people enjoy and where I can put them when I hire them.
- (continued) Answerer: I agree with the article that we are not strictly one type. It is a spectrum and it is important to understand that. It does not mean that we do not fit into categories or that we do not value things differently. I also agree that the coaching industry that is been built up around this is total garbage. But let's not throw out everything because of some scammers trying to take advantage of people. I have personally found that personalities make a big difference in what type of job people enjoy and where I can put them when I hire them.
Someone then raised a flag against the (referenced) comment about the MBPT being bunk.
At that point, I had several choices. Was the comment constructive? It was certainly constructive to the conversation. I could have left the entire comment thread alone, dismissing the flag. However, I tend to try to respect the opinions expressed by the community through flagging (that's part of how a community participates in self-moderation.) It's very unusual for me to dismiss a flag.
The entire comment thread was all about a personality test, which was not pertinent to the OP's question (How should a parent advise a child who wants to become a musician even though he is devoid of talent?) So the entire comment thread was deleted.
The next part is the one you question. Why did I remove part of the answer?
In this case, a user (not me) supported an argument that the MBPT was useless. By removing a flagged comment against the MBPT, I thought the fairest way to resolve the conflict was to remove the part of the answer which states (in an unsupported manner) that a personality test could help the OP decide what things his son might enjoy other than music.
It's definitely a judgement call, and meta is the right place to raise the question, so I'm glad you have raised the issue.
Probably tipping me in the direction of the edit:
A lot of the answers on this site are unsupported opinion. Since babies don't come with a definitive instruction manual, parenting to a large extent will be opinion-based.
I myself would like to see more answers on this site supported with a bit of research, especially when they espouse a course of action which may or may not really address the OP's question. That does influence my moderating.
Had the user rolled back the edit, I would have been fine with that, since I was on the fence anyway. Had the user supported his recommendation in the comment thread, I would have edited that into the answer after removing the comment thread.
So, as I mentioned before, it came down to a judgement call. I didn't actually remove part of a user's answer because I didn't agree with it (there are many things with which I disagree stated in answers. If I removed them for that reason, that would be vandalism.) I hope that you can see the comment on the edit in light of the whole picture. I see in retrospect that it sounds harsh. For that, I do apologize sincerely.