I know there is an answer to this question somewhere but I can't remember where, and I know it must get asked a lot, because I've asked it myself before now (hence I know the answer is somewhere), and I just had a friend tell me she may have done so, to which I gave the reply I was told.
When you click the "Report to Moderator" link, I'm reasonably sure it comes up with a dialogue screen asking for the reason you are reporting the post.
At this point, if you clicked the link by accident, you can back out with no one any the wiser. And if you didn't get that dialogue screen, then you didn't click "Report" by accident.
Am I correct?
And if so, please could this information be put somewhere helpful - or alternatively please could someone point me to where it is? I'm sure the question must get asked frequently, because it is quite easy when using a phone to read posts to accidentally tap the wrong thing, or at least think you have.
[Edit to add] I just clicked "Report To Moderator" on this post, which I figured would be easy to explain, and it does indeed come up with a confirmation screen with a comment box on. I then backed out. If I'm correct, Mods should only know about this because I'm saying so here?