I’ve seen it as well - mostly on ROS Answers and github. I don’t really mind, if it’s not too in your face.
But it should also not be the other way around (almost ‘covert’), which is something I’ve seen more recently: posting links to tutorials/blog posts/repositories that on the outside look independent, but turn out to be directly tied to commercial interests, without the poster mentioning this. Some recent ROS Answers posters have done this.
Obviously I’m not against anyone making any money, but I do believe that if you do something like that (ie: use something akin to product placement to expose unsuspecting readers to your product) it would be nice to add something like: I’m posting this here which will probably help you, but just so you know, I’m affiliated / working there / the owner of the service.