Where does this style work?

It works wherever plain text is accepted — bios, usernames and comments — because the letters are real Unicode characters, not a font.

Can I copy it together with other words?

Yes — copy the whole output and paste it next to plain text; every letter stands alone.

Bold serif italic — double emphasis

Bold italic combines the bold and italic mathematical blocks (𝑨-𝒛) — double emphasis with a book-like serif weight.

𝒀𝒐𝒖𝒓 𝒕𝒆𝒙𝒕 𝒉𝒆𝒓𝒆