Seems like a good general advice in most cases
A tiny improvement for a huge group can outweigh many drawbacks for a smaller one.
I don't think that HTML has this problem so much, but it's absolutely an issue with both CSS and JavaScript.
> Greetings, programs! Oh, what an occasion we have here before us. Because your rumors are true. We do indeed have in our midst a User!
(Can't find the 1982 quote, but this one from some 2010 redo gets the point across)