I notice that a lot of comments are really answers to questions - or at least could be considered answers to questions - should "one" submit a comment instead of a question when "one" is a little unsure of the answer? Is this a better use of comments than blurting out the answer?
I believe the Stack Exchange team's official stance on this is, "comments are for clarification, answers are for answering" . I often see perfectly valid answers in comments, which should really be answers. It's OK to go back and make your answer better later, and if you want to encourage others to spice it up, it's OK to make it community wiki and add a comment encouraging others to help flesh it out.
Remember, Stack Exchange is all about providing answers to questions. The reason comments are a privilege reserved for those with at least some reputation is because it's seen as an auxiliary feature. Comments are great for clarifying, and in some cases are good for "have you tried..." comments which could become answers, but if you know the answer to the problem, post it as an answer. That's how it's supposed to work.
That being said, as Ivo mentions, if you don't actually know, it might be better to post a comment with a suggestion. There's a fine line though between "somewhat unsure" and "making it up as you go along". It's alright to give an answer even if you aren't 100% positive. It sort of comes down to a balance in quality - one-liner answers which don't add anything probably shouldn't be said as a comment or an answer, but a brief answer can still be very useful.