Ask HN: User IDs in app share links

A thing I've noticed recently is more and more apps including some sort of "share id" query string parameter when you copy a link to share content.

These parameters are then (sometimes) used to surface a banner in the app when the receiver of the link opens it. Something like "user so and so shared this with you, want to follow them?". I'm presuming they are also used for ad/data mining/network building purposes under the hood.

For example Instagram adds an `igsh` parameter to share links while Youtube and Spotify add an `si` parameter.

I guess these are a continuation of the `utm` type parameters used for marketing. But they feel a way more creepy and invasive when operating on a personal level than a marketing campaign level.

Also the user isn't made aware of this parameter at all. A user link could get sent onwards and would identify the user as a source long after they are out of the loop.

Any thoughts on these practices? Is there an opt out somewhere?