Are there any good reasons to do that? I think focusing on username and then internally searching with the user id to not miss posts (due to name change) is better than using uid.
I also prefer searching the userID instead of the username. Numbers are easier and it saves having to copy/paste "complex" names.
Would you be fine with searching the user id and getting the matching username?
i.e
https://beta.ninjastic.space/users, right now you type Loy and LoyceV shows up. You would type 459836 (your uid) and get the same LoyceV result.
Or do you prefer something more direct: type 459836 -> enter -> goes to your user page?