[ReptileMan]

They use AT command set, not protocol.

[icedchai]

I've heard it referred to as "AT command protocol." I googled it myself and this terminology is common enough.

[account42]

... which is a protocol, thus pre-existing colloquial use of "AT protocol" that makes this trademark questionable.

[kube-system]

The mere "pre-existing use" of a word or phrase does not disqualify a trademark.

Maybe you're thinking of prior art in a trademark? Or trademark genericization? But neither would apply here.

[wat10000]

Is this a real thing? I don't think I've ever heard "AT protocol" before Bluesky. My first modem was 300 baud, so I wasn't totally out of the loop on this. DDG finds four hits for the phrase before 2020 used to describe the Hayes command set.

[steveklabnik]

It is an incredibly common comment to be made on posts about atproto, so there certainly are a lot of people here for whom it was a thing.

[wat10000]

I did a search and there are like three such comments in the past year, including this one.

[steveklabnik]

Depending on how you search specifically, you may or may not get all of them. For example, if you searched for "at protocol" specifically, you wouldn't get comments that are like "I thought we were talking about the old modem protocol!" and similar.

Anyway I don't think that it means that atproto was misnamed or anything, just that this thread isn't the only time people have brought this up.