Off topic but why refer to it as $DAYJOB (is it really a variable like that?) rather than just saying “work” or “my job”? I see it all over HN but I’ve actually never understood why people do this. Sorry for veering off topic.
The syntax is written like a bash shell variable, the idea (I assume) is that the actual job itself doesn't matter but the idea of it being something they do for work does (because contextually it means they have less decision power.) So, if it were me, saying I work for Puzzmo is about as useful as me saying I work for $DAYJOB in a sentence like that.
Nah, there's no need to apologize. If folks don't want to read and/or participate in the subthread that changes the topic, then they can just fold up the subthread using the handy "fold up the subthread" button.
And yeah, with the exception of the fellow who called it "HN slang" (or whatever) the folks who replied to you all have good answers to your question.