The author of the post probably accidentally hit the Compose key before comma by mistake. Compose comma comma produces that character.
https://en.wikipedia.org/wiki/Compose_key
A very NetBSD mistake.
https://en.wikipedia.org/wiki/Compose_key
A very NetBSD mistake.
It seems to be a cedilla, which is generally placed under the letter "c" like so "ç".
https://unicode-table.com/en/00B8/