Editing is a privilege that is earned once you have 2000 reputation.
Until you reach that point, you have to submit edits to the suggested edit review queue, where people with the edit privilege can review your edit and accept/decline based on their assessment. There is a minimum amount you must edit a post to get into that queue.
Obviously the edit you ...
Yes. More generally I think it's a good idea to create a sitewide close reason whenever we find that we're having to create the same custom close reason (Off Topic + Other) over and over again.
The proposed close reason can be slightly expanded to cover analogous situations where a person asks an English related question arising from an error or ...
They would have different meanings
How to not be a spammer
On this page I would expect to see advice for how to avoid being a spammer.
How not to be a spammer
On this page I would expect to see advice for how to avoid being a bad spammer. Gotta make sure your spams are lit!
If it aint broke then don't (try to) fix it
say the Americans and they are absolutely right. "How to not be a spammer" deals with how somebody should take care to not be a spammer. "How not to be" might well be the more widely used construction, and could probably be used instead without significantly changing the emphasis or meaning of the statement, but ...
You have two questions here:
Is “how to not be” grammatical?, and
predicated on (1), how can that wording be changed in the help center?
How to not be ungrammatical
For a fuller analysis of the grammatically of this wording, you should ask on EL&U Main. Meta is for settling matters about the site, Main is for settling questions about English.