SLAMITCH: taky mi to vrtalo hlavou:
"Two aspects merged here:
Triple parens is commonly used by antisemites and general "ew! Jew!" racists as dog whistle for jews. Such as "(((Bankers)))" meaning "Jewish Bankers"
One canonical use is applying that to the capital THEY, as in "THEY are watching us" as general paranoia. Change it to "(((THEY))) are watching us" and it's "... wink wink the jews, as all good and sound übermenschen know"
The second, originlly unrelated aspect is choosing non-default pronouns, common for non-binary people. In many places, such as a Twitter bio, they are commonly mentioned as "(they/them)".
Combine these two and you get "(((THEY/THEM)))" as indicator for a non-binary jewish racist.
Yeah, apparently, that's the joke."
Source:
https://www.reddit.com/r/ExplainTheJoke/comments/197963m/i_assume_the_nonbinary_is_probably_because_of/