Guideline-lawyer! :-) I assume that by
post, you mean
comment.
Please don't submit comments complaining that a submission is inappropriate for the site.
(1). I suggest that the "intention of the guideline" is to reduce cluttering the site with meta-discussion, and it would serve this purpose best if comment was construed as including a submission.
(2). in terms of the "letter of the guideline", what is the meaning of the words comments and submissions? The guidelines have separate sections for each, and clearly use the terminology used else on the site, which talks of comments on articles and articles that are submitted. A broader construction of "comments" as "things that comment on other things" is not the literal meaning.
Therefore, I agree that the excerpt about comments does not include submissions, and I was wrong. However, I think it should include submissions. :-) Another argument is that submissions about the site are not "On-topic", by this definition:
On-Topic: Anything that good hackers would find interesting. That includes more than hacking and startups. If you had to reduce it to a sentence, the answer might be: anything that gratifies one's intellectual curiosity.
I'm not sure that complaining about the site, and attempting to modify other people's behaviour, gratifies one's intellectual curiosity (in contrast, a discussion about how a social site can be run does do this).
However, I think in future, I might leave all such discussions to my betters, and focus on things that I find interesting, instead of trying to "improve" the site.