On /r/osureport/ subreddit it's said to use player's ID, while posting reports, instead of nickname, but the problem is that both nickname and ID link have the same beginning: "https://osu.ppy.sh/u/"

I started wondering, what happens, if someone takes a string of numbers as a nickname?
I tried to find some users with numbers as a nicknames and I noticed that if I can find an user with a number as a nickname, then almost always, writing these numbers in a link, brings me to this player's profile, instead of profile with such ID. For example:

https://osu.ppy.sh/u/2010011
https://osu.ppy.sh/u/50000
https://osu.ppy.sh/u/1000

There are exceptions, like game suggesting me that there is player named "108" (http://puu.sh/t5sQ9/99ddea479d.png), but it actually links me to the player with such ID: https://osu.ppy.sh/u/108 . Can't explain this, but maybe the player is just restricted or it's not always username over ID?

_ _ _ _ _ _

This makes me wonder: if there are active players with player's ID being taken as a nickname by other player, like 1000, 50000, etc. what will happen? Are such profiles accessible through /u/player's_ID link?

1. Is it always Nickname > ID ?
2. Or maybe it's something like "first come, first served", unless player gets banned, so the order matters?
3. Can you really change nickname to someone else's ID and redirect links to your own profile?

Let's give an interesting example:

When I visit store and check, if nickname "124493" is available (Cookiezi's ID), the page says that it's already in use. However Rafis' ID is free:
http://puu.sh/t5s2I/7eda7507ad.png

If I was to pay and change my nickname to "2558286", then links to Rafis' profile that contain player's ID would link to his or my profile?
Could there be a situation, that someone changes nick to "2558286", or just an ID of some known player, and the links from leaderboards and other places would link to his profile, instead of the player with such ID?

I don't ask, because I want to hijack references to profile of Rafis or someone else, so they would point to my profile instead, but because I wonder, if it's really save to report players with links containing their ID. It could be bad, if there was such a conflict, especially if some players, just for trolling, would start changing their nicknames to IDs of top #100 players.

If I recall correctly, the "display name" of the username only has a play when it comes to the profile page, or https://osu.ppy.sh/u. For generally any other purpose, such as adding a new friend in the Admin CP, map ranking, forum post searching, whatever, the user ID has precedence. So the only thing is that the profile thing just has a logic for username first, then user ID...

Users that get their username taken also get suffixed with "_old", or "_old2" if the previous one was already taken. They can't be searchable through the old site's /u/ link, as "_old" gets ignored, but it's searchable on new.ppy.sh.