These are in fact two separate accounts, but I was genuinely confused for a bit. I think I figured out what he did though

He exploited the fact that in Arial font capital i and lowercase L are exactly the same.

Look at these and try to see the difference

I l

You can't. There is none.

So on one account the end is an i

One is shorter than the other.

Barely.

At a glance you won't be able to tell

The I is shorter than the l

-_-

I saw it first glance

F*ck

I is thinner

I know
I gave him the idea to do that