Charitably, your profile indicates you have been 'subscribed' (or what ever they call it) here for 10 years. During that time you've posted reasonably often and received a varying amount of engagement.

> Thanks. I have, or had, no idea, not even zero, why my comment was flagged.

In that time I would expect it to become clear that anyone, at any time, has a fixed set of options when responding to a post:

1) Ignoring it.

2) Voting on it "up" or "down"

3) Flagging it (which generally brings it to the attention of moderation)

4) Commenting on it.

(note that 2, 3, and 4 are not mutually exclusive, you can flag, downvote, and comment all one the one thing).

Generally the reason for down voting or flagging is how your comment was 'heard' by the person reading it. Some folks down vote when they disagree, some when they feel it doesn't add anything to the conversation, sometimes because they feel it disparages or insults something they value. There an innumerable number of ways people can feel when they read something.