I've been marking flags on a lot of the spam questions that have been popping up over the last couple hours (the ones about bam war or something), and I accidentally marked one as offensive instead of low quality. I don't want that flag to be rejected because of the way it was marked (nor do I want it to show in my profile that I had a flag rejected). Is there a way to edit my flag?
Medica's advice is what I would give.
There is no way to change the type of flag that has been cast. In future, though, please flag spam with the spam flag, not "low quality". Not that we would mark "low quality" as wrong, but if you flag spam as spam, the post will be deleted sooner.
To put your mind at rest, though, if a post gets shutdown through validating spam flags, then any other flags will be validated, too.