Some people will base their decisions on which software to try/use, based on the general sentiment of discussions on Hacker News. For example, suppose you suddenly had the need for Email As A Service. Which of the plethora of services will you choose to use? I believe a lot of Hacker News users will weight their decisions at least in part on HN comments discussing those services.
The same goes for Firefox. If all people ever see is criticism, that is likely to drive people away from Firefox. That means less revenue for Mozilla, which means a worse browser for us.
Basically I'm saying that compliments, positive comments, are not useless. Quite the opposite.
(Don't get me wrong. I completely agree with you that criticism is necessary. I'm not saying those comments are bad. I'm saying positive comments serve an important function too.)
And besides, suppose you were a Firefox developer reading these comment threads. Don't you think the positive comments can provide a bit of encouragement?
Mozilla should know not only what it is doing wrong, but also what it is doing right. And that goes for any software and any company.
By that measure, they will completely turn off their computer because every single product is primarily criticism here. I also think substanceless praise is mostly useless in this forum (not in life) and I appreciate everyone here that points to specific points and issues instead of needless bloviation. I think encouragement, praise, etc can/should occur elsewhere and we can get to the meat of the product. It's like complaining that your QA team never opens JIRA issues saying you did a good job...that's not the best use of that communication platform.
What is different about "life" that makes substanceless praise useful?
I hope that your manager doesn't think that way. :)