I'm not talking about those "use the HCG diet, it will change your life!" people that bluntly advertise their product all over the site whenever some says "calories".
The case I'm referring to is a bit more subtle, in that the user doesn't really spam, but keeps recommending products of a single brand in a way which makes me think he might just be here to advertise those products. The answers of this person are not bad per se, but seldom provide more information other than "this (BRAND)-product should provide what you're looking for".
So what's our code of conduct regarding such users? Should one just treat their answers as normal, i.e. ignoring if they're okayish, downvoting if they're bad? Or would we want to discourage that form of advertising by downvoting more aggressively?