I don’t really like property_threshold ... with the output of « 0 (0%) » there is no way of telling whether this is an actual zero

I agree - I cannot imagine a situation where I would need this.

Looks good, thanks.

I've made progress on this. The page already calls a template ("Coloured cell") per cell, so my concern about template limits is irrelevant. So I decided to go with your "option 2", and made a helper template to generate these links. It has been set up as a wrapper for Coloured cell.

Or if that is too much, scrap the counts entirely (a percentage is already clear), and add two links with the symbols + and -. So it could end up simply as "86.56% (+ -)"

In the brackets you already show the number of items with this property. Hyperlink that. The second link for the negatives could also be in the brackets as a count, so it might look like "86.56% (2300:357)" where both the 2300 and the 357 are hyperlinks.

Does wikidata have a limit on how many templates can be on a page?

Thanks