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.
None the less, in the interest of discussing question (2), which is about the site, I’ll post this brief summary of the English question here:
And in the COCA, which is probably the most widely-used corpus of English, which collects a series of professionally published works, including fiction, popular magazines, newspapers, and academic texts.
I think suffices to bring into question (1), which is the premise of (2).
How to not be irked by the help center
Parts of the Help Center can be changed by elected mods on EL&U; but the parts that are universal across SE sites can only be changed by StackExchange employees.
Given that the language “how to not be a spammer” is an example of the latter language, to change it for the domain english.stackexchange.com, the SE elected mods would have to bring a case to the SE Community Managers.
But if it’s ungrammatical, presumably you’d want it repaired wherever it’s used in SE help centers, not just on the
english. subdomain. For that, you’d have to bring the case yourself to Meta.se where both the Community Managers and broader StackExchange audience can see it, weigh in on it, and make a final determination.
Note that for either the
english. subdomain as a whole or for a more universal change, you’ll have to bring a case that “how to not be” is ungrammatical. That is, as I said, your question (2) is predicated on question (1).
And, given the nGrams I evidenced above, the premise in (1) is looking none too healthy.
How not to believe English speakers speak English
But if the spark of prescriptivism burns brightly in your soul, and you are dismayed by the absolute ubiquity of this usage, then your best bet is to ask (without prejudice) on EL&U main and let our resident grammarians make a case one way or another.