Without weighing in on the merits of the comment, the delivery feels very Poettering-esque.
BUT the convenience methods defaulting to "standard" base64 instead of "url safe" base64 because it's one of the things where people don't think about there being more then one standard/configuration and it then loading to bugs in their code
so deprecating it makes sense, and without a braking change (which makes no sense here) you can't replace it with anything better
and because of the prelude module the import isn't that bad e.g.: `use base64::prelude::{Engine as _, BASE64_STANDARD};`
and even ignoring that most imports are auto generated, sorted and formatted by rust analyzer for most people most of the time
so it's eitherway at most a minor anoyence
so I can understand that the author is feed up with people annoying him about that again and again and again
And in fact there's others who would make a counter argument that excessive reliance on traits is a bad over-complexity-smell.
The reality is it's fairly large language community already, and lots of people have lots of different opinions.
People behaving poorly on github issues/PR discussion is so common in every language it tells much more about the internet/open source culture than it tells about Rust users (there's no such thing as a “Rust community” nowadays BTW, it's not 2016 anymore and the language user base has grown so much the user base is now as fragmented as it is for any mainstream language).