Currently, can you lose the onyx?
I have seen many onyx that play very badly and many others that lose constantly, and still have that rank.
Yes, you can drop back down into Diamond.
Yup, you can drop below Onyx.
Yeah you can go down but sometimes it’s only by 1 or not too much
You can drop, the problem is that with a small population and this True skill 2 system a lot of people can lose and only lose 1 point. This effectively makes it where losing has no consequence
People have good & bad games, if they keep playing bad they’ll eventually start going down. If you’re playing well, you can keep losing and only lose the 1 point as others have commented, and you’ll gain back more than that for wins.