aestheticsymbols
Use in a combo

Double down-right corner copy & paste

╔ is double down-right corner, a plain-text Unicode symbol from the Box Drawing block. On Aesthetic Symbols it lives in the borders & shapes collection. As plain text it takes on the font and colour of wherever you paste it — a bio, a username, a caption or a stream title.

Unicode
U+2554
HTML entity
╔
CSS content
\2554
JavaScript
\u{2554}
UTF-8 bytes
E2 95 94
Made of

U+2554 ╔ · Box Drawing

Will it show up? · Long-established text symbols

Plain-text characters from blocks that mainstream desktop and mobile fonts have covered for years. These are the safe ones.

Worked out from how each character is encoded, not from a test on a real device.