I think the no promotion rule is good, though I’d argue that we should just keep it as “no promotion of off site content in this community.” Effectively enforcing the no promotion anywhere rule would require relatively invasive moderation, and could lead to inconsistent enforcement and arbitrary hair splitting.
Controlling what people can do here is fine, but trying to dictate what they do elsewhere seems unnecessary.
It happens to me very occasionally, specifically with circular toilet seats instead of oval toilet seats. There’s one toilet at my dad’s house that gets me every time.