A caret with a character subtracts 0x40 from its hex value allowing you to insert non-printable characters. Uppercase H is 0x48. That gives us hex 0x08 which is a backspace.
Ctrl-H is the rubout/backspace command on old terminals. So if I say it's nuts^H^H^H^Hunwise to ignore UNIX history, I've erased the first word and replaced it with the second.
In the old hardware terminals, and current terminal emulators, ^H (or CTRL+h) is "Backspace signal". It has the effect of pressing backspace.
So, ^H^H^H means "delete three characters, excluding '^H's". Like the person typing the comment changes their mind and deletes the characters (or the word) before writing else.
It's an stylized way of euphemism. i.e.: Actually I want to say this, but I substitute it for that.
https://commons.wikimedia.org/wiki/File:USASCII_code_chart.s...