I do mean to express dislike, as I'm one of the millions of users giving Wikipedia a false metric and sense of satisfaction. I've seen the pop-up hundreds of times, and have considered it a hindrance to my process every single time.
Something that just happens accidentally is a bug, no matter how useful it might be if it were not happening accidentally.
When you go from reading the Atlantic, The Economist, The Washington Post... any content site... then begin to read a Wikipedia entry everything you know about reading an article no longer applies. You are now forced to change what you do.
This is just the most basic no no in web design - unplanned interactions, forcing a user to interact, forcing a user to actually think about the interface.
The developers have just forced every person who wants to consume content on Wikipedia to do it differently than on every other content site.
And there are literally countless millions of people who will have no idea how to disable it, who use computers every day but have no idea how to change something.
Something that just happens accidentally is a bug, no matter how useful it might be if it were not happening accidentally.