I put the siren emoji in my signature and refreshed the page after applying changes, and my signature was gone.

That's why it's empty :/
It's because it wasn't a support emoji. I believe that's just how the forums work with invalid emojis.

Most of them are outside of the Basic Multilingual Field(hat ever its called)

scratch no like un-supported emoji in forum.
what scratch do when un-supported emoji?
scratch delete every single character after the emoji, even emoji itself.

We could still add emojis like “_Meow_”

ByakuyaTheDog wrote:

(#5)
We could still add emojis like “_Meow_”

That is for comments, please stick to what the OP is asking.

ByakuyaTheDog wrote:

We could still add emojis like “_Meow_”

no you gotta do it like

there’s only very few emojis that scratch supports, so with the ones that it doesn’t, it just removes everything in the post/sig after the unsupported emoji