The answer was indeed not helpful since the ~ are absolutely fine, as you pointed out. I have now deleted it.
Next time, if a post requires attention and none of the standard flags fit (or are available to you), just raise a custom mod flag letting us know what the issue is. That way the mods can take care of it.
Moderators only get "Helpful" or "Declined" for flag states. In this case, I marked it as "declined" because at the time of the flag being reviewed, it was not valid, and I didn't find the flag to be "helpful"
There is no such thing as "clearing" a flag so it doesn't exist unless you retract it yourself (though the flag becomes "Retracted" in your flag ...
If you do not want to close the question as a duplicate, then do not use the duplicate flag. Simply leave a comment with the link to the related question instead, then it would appear under the 'Linked' section at the right.
Once you flag the question, it goes to the close vote review queue (accessible to users with 3000+ rep) and then it requires action ...