If anything, this was a very short and quite contextual piece of text-only advertising. If all online advertising were like that, I won't have to run an ad blocker.

No need to do that. The provenance does not matter as long as the content is interesting, which is the case here.

This is the original hacker's ethos: put something out there for others to use, and let the people make their own opinion about the thing itself, not the authoritativeness of its source.

As long as it's not apparently being done by a bot, who cares?

This is effectively an advertising website.

For me, undisclosed self promotion puts a very bad taste in my mouth, to the point of coming off as bad faith. I dislike pretending you're just mentioning a cool service since you're effectively trying to trick me with false social proof.

If the post had said "I made xyz which could auto generate domains for these ideas using ai to fully close the slop gap" I wouldn't mind and might even appreciate the additional fun.