Bullshit.
Your overall comment might apply to a consumer facing website, but your feedback is rubbish for some developer providing a proof-of-concept. mckirk made a perfectly good "fyi" comment because it didn't pressure the dev, while giving the dev a heads up _if_ they are interested and happen to read HN.
Firefox on a laptop is now a niche browser (3.35%) and is trending to be less popular than Opera (2.86%) and Samsung Internet (2.6%). Obviously HN selects for abnormal users: I actually like mckirk's comment because it is a beautiful reminder that there are niche users with interesting configurations and maybe I should have a look at that plugin. Nobody wants to be an entitled open source user.