I'd encourage us to adopt a style of "link only the first time, but feel free to break this rule if it aids comprehension to do so."
Like, if you mention a card once and then mention it in a different context four paragraphs later, linking to it again is no big deal. Because readers might forget about the card's little details by the time they get to the second reference, or skim to the part of the answer that seems most relevant to them. That's not a link anyone should remove for the sake of making the site "more proper."
However, linking every single instance is likely to overload the reader, as Malco points out, and it actually gets in the way of understanding by making it harder to recognize "oh, I just read about these two cards already two sentences ago, only this third card is a new thing I have to look at."
That means that, in the overwhelming majority of cases, you're probably going to only link once. Since most of our answers aren't, like, ten paragraph essays. (Some, however, are ten-paragraph essays.)
For example, if you've got a decklist, it makes sense to linkify all of them instead of going through to identify which are first references.
"Why is Jace, the Mind Sculptor, banned in a bunch of formats?"
[paragraph of text discussing CawBlade] Note the interaction of Jace's Brainstorm-like ability with other cards, like Squadron Hawks, which can functionally turn "draw 3, replace 2" into a pure "draw 3."
[later on, you present a modern-day Legacy Countertop/Miracles list to explain how JTMS holds up even in an environment where average card power is amazingly high so the rest of the deck doesn't need filler just to make Jace better]