Below is exactly what you see. There really is a use for each one.
A comment is just a comment as stated, it does not alter the state of the suggestion in any way. The status of the suggestion remains the same and it isn't going away. A comment without correction is used when/if there is no known remedy for the suggestion, but there may be one in the future or it needs to be referred to another person to remedy.
Not corrected is pretty clear. With or without a comment the status hasn't changed and the suggestion isn't going away.
Corrected means just what it says. You believe you've corrected the problem and the suggestion will disappear until the next check with or without a comment. When the next check rolls around, if you haven't actually corrected the issue, it will come back and you'll need to rethink what the correct approach to the issue is.
False Suggestion might lead to confusion but I'm not sure what else you might call it. It's basically saying the suggestion made isn't a problem because it may look wrong but it isn't. Checking this, with or without comment, makes it go away forever as stated. It should never be used just to make a suggestion go away. It should always be used if the suggestion is wrong.
Proposed merge is used for suggestions involving duplicate profiles. Most merges will be completed within 30 days so the suggestion should stay gone. If it doesn't, the status of the merge needs to be checked and either completed or any issues holding it up resolved.
As Melanie pointed out, the comments to the right as you select a radio button are simply suggested comments based on the frequency of use of the comments. They aren't written in stone, can be used or not and make no difference at all to the status of the suggestion. If you want to make a comment and don't like any of the suggested comments you can write your own or leave the comment field blank. Comments are for the edification of other members, nothing else.
Select a status:
Comment (no change in status)
Not corrected
Corrected (hide until next recheck)
False suggestion (hide forever)
Proposed merge (hide for 30 days)
Optionally, include a comment: