:)
How much would a person's rating go down if black moved first?

you know that it would be the same right?
Right.
But I've heard of using this as a sort of trick though. A coach will show a student a well known middlegame position, with colors reversed, and ask them what the best plans are. Sometimes the student wont recognize it, and come up with bad plans. (which means they don't really understand the position).
Yes but ther fact moving first would have nothing to do with that I think, am I wrong?
If black moves first, the biggest difference would probably be that the kingside is on the opposite side, which could be disorienting at first. Also sometimes when you get a reversed opening, and black is the one with more space or development it can look a little odd.
But yeah, it's really the same game of course.
Ok but i'm smart enough to realize the differences I asume most of the other members are as well.

then how would it affect your rating? if you play just one game?
by the second game most people would have adapted.
my understanding of the ELO formula is that it returns more accurate results over time after more games have been played.
Your performance throughout the game.

ok, so you invented a "variant" that you can play once, good job!!
Please stop trolling an actually answer the question. The question relies on playing this only once. If you make another troll post, you will be blocked. Thank you.

It would definitely make some positions look weird.
I don't think it would hurt that ratings much though.
And after a day or two of playing I think you'd get used to it.
We are talking about this scenario: You have no preparation for this variation of chess, and it's a two minute game.
My openings are pretty boring, so I don't think it would matter to me. At most I'd need a few extra seconds to orient myself... e.g. I know d4 is important but in this game it's actually e5.
And once it reaches a middlegame I don't think it would matter at all.
Also, 2|0 games are full of system-like openings... like a london or colle, so I think there's also a good chance my opponent would be playing something that can't punish you if you mix up the move order.
Proof of this...e5 is not the same as d4.

Seriously, at a short time control, without every preparing for such a game, he wouldn't spend at least 15 seconds trying to figure things out? We are talking about the whole opening stage.
The weak will be the weak. The strong will be the strong, and the stupid will be the stupid.