It comes from an alt-right podcast, where rather than outright say “this person is a jew and jews are bad”, they started making the names of jewish people (or those they suspected of being jewish) echo dramatically so they could have plausible deniability. The textual form of that echo became (((this))).
On places like 4chan, it’s used as a kind of dogwhistle. For example:
I think the internet gets stupider every day at this point.
It comes from an alt-right podcast, where rather than outright say “this person is a jew and jews are bad”, they started making the names of jewish people (or those they suspected of being jewish) echo dramatically so they could have plausible deniability. The textual form of that echo became (((this))).