I think a lot of the issues people are having stem from the same basic issue: It is treating all tags with equal weight. However, I think special consideration ought to be given to "orientation" tags.

That is, the gender tags, the form tags (anthro, feral, humanoid, etc.), the gender-on-gender, gender-on-form, form-on-form tags. They should carry a special weight.

I'm not sure exactly how the "experimental" modes work, but I think one way to do what I'm suggesting would be to always include at least one of those tags from some favorited image, and in particular, it should always take the highest-order tag possible from an image.

Which is to say, a solo picture containing a male anthro would have two "single order" possible tags - "male" and "anthro". A duo picture containing a male anthro with a female feral would (if properly tagged) have four single-order tags (male, female, anthro, feral), and three "double-order" tags (male/female, anthro_on_feral, male_on_feral). So the way the program would work would be to choose from "male" and "anthro" if examining the solo picture but if examining the duo picture, it would ignore all of the single-order tags and only choose from "male/female", "anthro_on_feral", "male_on_feral".

The point of all this would be that, first of all, there would be a heavy focus on trying to match the user's orientation... But beyond that, this would also avoid issues where, if someone has, say, a lot of female solo pictures and male/female pictures, the program wouldn't see "male" and "solo" and figure "oh hey I'll give them a bunch of solo males!" when really the obvious conclusion from that mix of favorites is that their interests are just the opposite of that - a focus on females.

This entire post of mine is completely unwarranted but I am tired as heck and my window is being replaced so I can't sleep. Banging and noise, woo! Blah.

Anyway. I did want to offer some encouragement, to balance out what might be seen as negative... I do think this is a somewhat nifty project - I've considered doing similar things in the past, so I support what you're going for here.

And despite how picky I can be when it comes to enjoying art, This did actually manage to expose me to something I'd not seen before that I liked, which honestly even people who know my interests well can struggle with. So I do want to say "keep at it".