How is it determined which tags are shown at the start of the question in the title of the webpage?
This is related however the answer is incorrect as proved by this question which has no tag in the title despite "backwards compatibility" not being used in the question. Also by this question which has two tags. This question is similar, it has two tags similarly named to the previous one but only one tag is shown in the title of this one. Why is this?
So what determines how many tags are shown and which tags or why are no tags shown?
Note this question may be only applicable to arqade.