Shared links to posts contain user ids to be used for Announcer badges. These user ids are better to be stripped from all these links in SE posts and comments (and perhaps bounty statements), because:
It can happen that they will count towards the Announcer bage even if these links were published at SE: Got Announcer badge for linking within SE - either because users have referer disabled, or because the links have been captured by some web scraper (see the linked discussion). Stripping user ids at SE network completely will cure these issues forever.
It will save space, especially in comments. I mean, not only when displayed, but also at the input where the quota on the number of characters is applied.