I agree that good info in comments is a bit of a waste sometimes. But people should be able to have free will to write what they want in comments (within reason and bound by the basic rules as per the comment flag options). When not a rule breaking comment, it's up to the community to decide if it should remain or not.
It's a matter of opinion whether a comment was just a basic passing note, additional info but not worthy of an answer, or otherwise.
People can just quickly share the info in comments, whereas forming an answer has more requirements for time and expectations.
I don't think it's fair to flag/remove them unless they're bad or useless. Moreso:
I have been flagging them and they are being removed
That means the info is now entirely gone. At least before it was present even if just in a comment.
The real solution to resolve wasted info and improve the question (and site) is to use that info from the comment and form your own answer from it. It's not bad etiquette to do this.
The commenter had the chance to make it an answer and chose not to, but if you feel awkward about doing it you can give the commenter credit, and/or make the answer a wiki post.
So if you feel the info is worthy of an answer create one and expand on it to make a really good answer. Obviously, just don't copy/paste.