I agree with others that editing suggestions could be problematic, but that isn't what OP is asking - being able to edit your voting comments wouldn't neccessarily impact much, so I'm all for it
Many have concerns with abuse of this potential improvement, but it would address a real issue. My suggestion is that edits must be submitted to an admin, who then decides whether to publish them.
Maybe you could edit the suggestion before it gets votes? If people could change anything about their suggestion and completely rewrite the entire thing after people have voted on it, the feature would almost certainly be abused.
At least you should be able so delete it, and voters get their money back. But change a suggestion when it got votes is risky.
I would probably be less anxious about adding comments with my votes if I could fix unintended/unclear wording, grammar errors, and spelling mistakes.
Typos bug me and I am also very prone to making typos. This would be helpful
Simple mistakes/omissions or additional thoughts very often occur to me soon after posting a comment, no matter how much care I think I've taken to write it and I suppose sometimes it could be worse than that. Just human nature. I'd also like the ability to edit my comments but I generally think the team is better focusing on core WA functionality ahead of improvements in this feedback system, so it wouldn't be an absolute top priority for me.