The second part is easy. We say "familiar to ...", not "familiar for ...". (Unless you're handing out demonic spirits to witches, in which case you might say, "And here is a familiar for Helga, and here's a familiar for Brunehilde ...")
As to the first, I'd be more likely to say "comments on the proposal" or "comments about the proposal". A comment is "about" something.
"For" is generally used when we are discussing purpose. Like "This knife is for cutting meat." that is it's purpose. Or, "This book is for you." It is intended to be given to you or to benefit you.
"To" is pretty vague, but generally indicates a direction. "I went to the store." "I gave the book to Joe."
So in this context, you might say, "He made a comment for improving the proposal" or some other indication of the purpose of the comment. You might possibly say, "He made a comment for the proposal" meaning that he said he was in favor of it, but that would be rather awkward wording.
You could say, "We added a comment to the list", or if comments are incorporated into the proposal document, you could say, "We added a comment to the proposal." In that case you're talking about where the comment is going: to the list or to the document. But you wouldn't normally say, "He made a comment to the proposal".