Not same emoji between channel title and text

Hello, as you know we can put in the channel titles.

But sometimes, the emoji is not the same between the text and the channel title.

Look instead : here you can see fire emoji, look the same between left and right

And here you can see that the astronaut and the comet don't have the same rendering between the left and the right.

I have this problem everywhere on web client Firefox 78 + Linux, Windows 10 or Android Client 10.