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If you can choose both, and assuming these aren't tags but a separate system, then that kind of incentivizes everybody to choose both to increase the number of search results their game turns up in, but itch's culture isn't quite that mercenary, so let's just set that aside.

Choosing both definitely makes it less objectionable, but it also seems like it would make it less useful. I just don't foresee a system like that pruning too many results unless you search for games that exclusively use one tag.

I don't imagine that tagging with both would help? Like by that standard you might as well tag your game with every genre too, or at least the popular ones. The thing is if you put yourself in the "artistic" side of things, people expect something from it, and you're theoretically "competing" with everyone else in that tag. Less of a concern for most artistic games than for commercial games. Meanwhile, good luck getting anything from tagging your artistic game as commercial. People will judge it on criteria it isn't aiming for, and at best you'll get a couple of purchases maybe? And then maybe refunds?

There are games that do both, and some successfully so. But they know what they are, they know what they're trying to do. They're not Slap Game trying to sell itself.