What I do remember unambiguously is being an active member of the site, contributing regularly and in good faith, being accused of spamming, and the general feeling of hostility that I got from the site.
But you're correct on the second part, there isn't a level of activity that entitles anyone to post a sales page with nothing to discuss on it. Your activity was taken into account, though. Typically if a new user's first activity is to post an ad I'll also ban the site or user. I understand the rules aren't as permissive as you wanted, but ads don't start good discussions.
IMO, the lobste.rs admin's assertion that the post had "nothing to discuss" is a misjudgment that undercuts the rest of their rationalization. My guess is that they're looking for a win on technicality, instead of addressing the myriad of concerns raised elsewhere in this thread.
I don't think the technical win you want is possible or even worth it.