From the FAQ:
Post good, relevant answers, and if some (but not all) happen to be about your product or website, that’s okay. However, you must disclose your affiliation in your answers.
We don't see all self-promotion as spam. As long as the promoted product is really helpful for the OP, and the answer is more than just a link saying "buy my product", we see it as a useful answer. The way I measure it is: If I knew of these people's product, but promoting it wouldn't have any benefit for me, would I have written an answer sugegesting that the OP try it?
I have seen lots of borderline answers including self-promotion, but I think this one is clearly on the good side. The mere mention of a product the answerer owns is not considered a problem.
By the way, if you see a different case where the self-promotion is uncalled for, but combined with useful information, don't hesitate to flag. In such cases, we generally remove the links and product mentions, but leave the rest. So no good info gets lost.