I found this answer which basically is an ad for a software that author made. It is clearly spam and should be marked as such. But no, my report was declined saying declined - a moderator reviewed your flag, but found no evidence to support it. Is there an explanation on this? Is spam allowed if it is related to Stack Exchange? Or is this some kind of privilege that some users have?
The flag dialog says:
Exists only to promote a product or service, does not disclose the author's affiliation.
The post is providing a workaround for the feature-request, so it arguably does not only exist to promote a product or service; it might help the author of the question or other visitors.
As for the second part, when you flagged (I've edited it since), the post started with:
Wrote a Chrome Extension
Now, proper English would be "I wrote a Chrome Extension" but in many languages (including Hebrew, which I'm guessing is the author's native language, based on their name and profile) the first person personal pronoun is omitted. So that counts as disclosure, and it's not spam.
Yes, if this author would promote their extension in the majority of their answers here, it'd be rather spammy, and in those cases, a custom moderator flag might be warranted. ♦ moderators will only see this single post in their queue, not the entire picture, unless they decide to dig deeper, which they are more likely to do if you tell them there are multiple answers involved.