I believe that it benefits language learners and fluent speakers alike for documentation to use the most common of the most precise words that fit the intended meaning. We have had several discussions about simplifying the way we write on ELL.SE, the most recent being Simple English please!. Our community has always settled on not "dumbing down" the vocabulary, but instead striving to avoid idioms, slang, and in some instances, complicated sentence structures.
So there are two issues I think we have to figure out. What is the intended meaning of
The community tends to vote down overt self-promotion and flag it as spam.
and is 'overt' the most commonly used word that conveys that precise meaning?
Overt is defined as 'open and observable; not hidden, concealed, or secret'. It is not in my opinion interchangeable with blatant or obvious, and I don't think we should muddy the waters by trying to change the intended meaning and incorporating covert in there (that's a discussion for a different question).
In my opinion, the community tends to not like self-promotion in general, and tends to down-vote overt self-promotion because they notice it and not because it's overt. I think overt is the correct word to use there, with obvious being the runner-up.
Regardless, I don't think a replacement word is going to add or detract significantly from the message, so my inclination is to stick with the status quo.