Like all good problems, the answer to gatekeeping is "depends".

What he talks about with the initialisms and such, essentially using shibboleths to exclude others is a bad form of gatekeeping. When addressing an audience that may not know everything, it's best to lead off with a definition, then use the initialism from then on.

For example: "Dynamic Host Configuration Protocol (DHCP) is the way a lot of devices acquire addresses on the network. The DHCP handshake is composed of four actions. etc." instead of "DHCP is how IPs are assigned: DISCOVER/OFFER/REQUEST/ACK".

Both statements say mostly the same thing, but the second is really informationally dense and hides information behind terms.

However

Asking how to perform juggle combos in Street Fighter is not an appropriate topic in a discussion about how to implement DHCP. We should be able to tell that guy to stand outside.

So part of a gatekeeper's duty should be to recognize when it is appropriate to bounce a person and when someone is trying to unfairly exclude others.