I'm the project lead of Matrix (as it says in my HN bio). (I'm also ceo/cto of Element, but that's less relevant).
No one expects you to read every bio of every comment you read, but conversely we shouldn’t expect him to preface every single one of his comments with “Hey guys, I’m the project lead of Matrix.”
Arathorn is very active in comments, and it’s well known to frequent readers he is the project lead of Matrix.
HN's minimalist post format isn't amenable to adding such disclosures all the time - but making them available in bios is practical.
You may also want to assume deep undisclosed conflicts may exist whenever there's no bio info at all – as with your user page.
Oh, for all the bigco employees to have their affiliations declared for when they're flacking their company interests under a pseudonym! Oh, for net upvotes/downvotes on highly critical/opinated posts to be cross-tabulated by employer conflicts! Unlikely, but things to think about.
But bringing up that you're the project lead of the project your discussing seems like an obvious step.
And, it often has the added benefit of more useful credibility context than just revealing blatant conflicts.
It's impractical to expect a commenter to consider, for every comment, "how much involvement in these particular topics should I declare?". That's especially the case on topics for which the commenter often comments, or multiple comments in related threads in a long discussion - where such a standard would be onerous for both the author, and the readers.
Add major affiliations to the bio, and I'd say you're covered for comments related to those affiliations, as it's then easy to check for anyone observing any partisanship, without encumbering all writing/reading with redundant disclosure-noise.
If you want scrupulous disclosure of relevant affiliations inline in every single comment where they could apply, I think you're in the wrong place.
As you note, it's not a site guideline. As I've noted in a sibling thread, it wouldn't fit the minimalist HN presentation, and would place an onerous burden on both writers & readers.
It'd also especially encumber people with deep personal knoweldge and interest in some topics, if every related post required boilerplate "I'm employed by X"/etc inserts.
But putting it in the bio for the curious/suspicious is a very honorable thing to do!
The guy gives up additional disclosure information and you see that as an opportunity to make smartass comments