I agree with you. The answer does not comply with the StackExchange policy on self-promotion. As the policy says:
Avoid overt self-promotion.
The community tends to vote down overt self-promotion and flag it as spam. 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.
The answer you link to violates those guidelines. It does not disclose the user's affiliation in the answer. (If you go to the user's profile, you can discover the affiliation, but almost no one does that.).
In addition, I consider the answer borderline deceptive. The answer states:
I use it and it really works like a charm.
As a reader, I would interpret that to imply that the person who wrote that is an unaffiliated user of the product. That just invites the reader to draw inferences that are inaccurate -- and the user who posted the answer should have known better.
I left a comment for the poster. I'm also reflagging this answer, given how it violates site policies. We'll see what happens.
Update: The answer has now been edited to bring it into compliance with the site policy. Therefore, I consider this issue to be fixed and to have a happy resolution. Thank you for your patience and for bringing this to the attention of the community!