It's not just a tracking tag on Reddit; the shared links largely obfuscate the thread or comment, requiring one to go through the tracking link to find out what is behind it. An example for anyone curious:

Tracking /s/ link:

https://www.reddit.com/r/Blind/s/xxQGmFcPSS

Leads to the following:

https://www.reddit.com/r/Blind/comments/17atlg7/my_6_week_ol...

Another pattern that I hate is that Reddit will create an account for you if you are using a browser profile that does not have an associated Reddit account. It will then prompt you to 'personalise' the username and password.