Comments can be edited during five minutes. After this delay, it can still be deleted. After the deletion, it is possible to repost the deleted comment with just spell-checks.
Is doing this OK?
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If a comment needs to be edited after the 5 minute window for whatever reason then deleting and reposting is the correct way to do this.
The only issue with this is if your existing comment has already been replied to; in which case you must balance the positive of correcting your comments to the negative of breaking the reply chain. If the reply chain is still relevant then it is best to leave the comment as is, if it is not then the entire chain should be deleted rather than corrected (you can flag the other side of the conversation as obsolete if this is the case).