Inspired by How do I get my game reviewed?
and in particular in response to
We also don't want people to link their games here, unless the game's content itself is material to answering the question. Otherwise that opens the door to questions that aren't really questions but phrased as such just to be able to advertise here.
I absolutely agree that advertising-spam would be bad, and that Not-Real-Questions should not be allowed here. I don't understand, however, why linking to a system that comes up in a question, particularly if the system is not well known, is considered part of the slippery slope here. It's a well established practice to link to systems covered in answers, which would seem more likely to attract spam, so I'm not sure why it's not allowed in questions. Do we have a history of spam problems or something? As far as I'm aware we've never had problems with egregious self-promotion, so this caution seems to me misplaced.
My answer initially suggested that the querent link the system they made to the text "Made a system" and "available free online", and I was actually surprised that those text parts weren't already links.
Note: I'm not really asking to change the policy. I'm asking for someone to explain to me (better and with more detail) why this policy is the case.