Recently I noticed that the software inserts the id of the currently logged in user in the “share” link of any MathOverflow question or answer. When one is logged out, the “share” link comes out normal, without any private information. For example, the same link appears as https://mathoverflow.net/a/198099/402 or https://mathoverflow.net/a/198099 when I'm logged in/out, and 402 is my id on MathOverflow.
I think it's safe to assume that users have a reasonable expectation of privacy with respect to links to publicly available pages, in particular, one does not expect one's own unique user id to be inserted in the link, allowing others to identify the user that posted the link.
One doesn't have to go too far to see that this type of surveillance activity is far from being innocent: an anonymous referee reviewing a paper for a journal adds a link to a MathOverflow answer in his report, e.g., in order to clarify something. Unbeknown to him, the SE software inserts his user id in the link, revealing his identity to the author.
What is the opinion of the MathOverflow community on this matter? Do we consider such type of behavior by SE to be acceptable?
Myself, I see it as an unethical invasion of privacy, especially because the users are not informed of this type of surveillance.