Early on I got one comment on one of my answers that it should have been a comment, at the time I didn't have the privilege to post comments, which seems really silly. Comments are supposed to be less important than answers, so why is everyone allowed to write answers from the start, but not comments?
Because comments are less important.
We only want to be getting comments from people we know can and will add value to the site, not just the grand internet peanut gallery.
Note that you can comment on your own question and answers to your own question from the start.
The answer to this is really the same as when we covered this in Meta Stack Overflow. So to quote that answer over here:
We funnel users to the answer input box for a reason -- because the focus is on getting answers to questions, not meta-commentary. Commenting is a privilege that should be earned by providing useful answers. And 50 rep isn't much.
It's highly unlikely a random drive-by user will
- understand our Q&A goals
- understand our commenting system
So by the time they earn 50 rep, they should have learned roughly how things work, and be in a position to offer a useful comment and not a "+1 AWESOME ANSWER" or "NO U R WRONG!!" sort of comment.