I'm in the same camp as the author in terms of this type of copy, not only having no impact on me wanting to use the product, but also feeling it is condescending and confusing and mildly pushing me away from the product.
But I'm curious if this stuff works overall. I guess it does? People keep doing it.
At my jobs I've seen bosses decide what works based on whatever they thought is best. How much do they get feedback from real users? Never. They're the boss so they must know what's right.
I assume this is the work of one major decision-maker at Mozilla who either likes this stuff or assumes that other people do.
This reminds me of the difference between Siri and Google Assistant when voice assistants first came out.
Google was always no-nonsense, no jokes, just giving you want you're trying to get. It doesn't pretend to be a person, it acts like what it is: a tool. It's a voice interface for looking up information and accomplishing tasks.
Siri, on the other hand, was a "person" that would try to respond like it was a person. Compliment Siri and you'd get a response saying "Thank you" or some such thing. It provided some entertainment when you'd ask Siri weird personal stuff and see how she'd respond.
Some people may like Siri, but I always found it tacky. It was trying too hard to be cute instead of useful. I appreciate the no-nonsense Google approach instead of Siri.
Perhaps the balance in these attributes have changed since they first rolled out, but the difference was very stark at first.
I remember freaking out when firefox introduced the "awesome bar" (what we used to call the navigation bar) some years back. The self-satisfaction in the term was revolting. Thankfully, I haven't heard anything about it recently.
But I'm curious if this stuff works overall. I guess it does? People keep doing it.