Or it may make more sense per cardset. You might have a shortlist of "This should be in modern templating", "I prefer to use modern templating, but these cards haven't been templated yet", "I prefer to use modern templating but with British spelling and singular 'they'", etc, etc. Obviously people should be able to do that by putting a comment in the cardset, but it might make it easier to have that option explicit, and possibly cut down on superfluous corrections??

Eeenteresting suggestion.

In reverse order: your #2 is something I've considered. I've actually considered it more for cardsets: in a view like Recent Changes, I often want to navigate to some particular cardset and create a card in it, or search that cardset's cards, or whatever. So I've considered adding mouseover panes for cardset navigation. For users also makes some sense, although I'd want to know it'd be some use before I put the time in to deal with it.

Your #1 does make some sense. I wonder though if it's too specific. There could be other things users might want to indicate before people comment, such as "This set is deliberately breaking the colour pie so there's no need to point out colour pie violations", "This set isn't using rarity so there's no need to point out inappropriate rarities", and so on. As Jack says, this seems mainly to be on a per-cardset basis.

I don't know how much of a problem it is at the moment with people being offered undesired templating advice. It seems similar to the way that most of the feedback authors of fiction and fanfiction get will be "You made a typo here and your grammar is wrong there", where what they'd prefer is more along the lines of "This character is underdeveloped and this scene breaks suspension of disbelief". There are certain types of error that it's just easier to spot (for certain kinds of commenter). I don't know if most cardset authors would prefer to have templating comments or no comments; it's often the case that one person making a templating comment prompts others to make more useful comments by drawing their attention to the card.

What I think I might consider is allowing a user to specify, on a per-cardset or also perhaps per-user basis, one short sentence to be shown to everyone who's about to comment, perhaps alongside the "Post comment" button. A few present options would be things like "Note: I'm not trying to use modern templating in my rules text", but it could also be free text input for any other points authors wish to make.