my take is... people do! but it doesnt come up like that.
i have comic friends whose comics i love, who like my comic too - and when i read and engage with their comic, im not just engaging with a comic i love, but also making sure my friend gets some appreciation. we didnt discuss this as a sub for sub relationship, its just a naturally occurring mutual respect. even with creators i dont talk to, if we follow eachothers comics theres a kind of mutual respect and back scratching in my mind. (though i have other comic friends who dont read my comic, and i dont read theirs, just because we have different tastes.)
i feel like unsolicited calls for 'active sub for sub' wouldnt go well because it happens naturally when two creators click - although some kind of virtual networking event could be interesting?
also, could be worth knowing - theres a system like this that people do on instagram. instagram pods are groups of creators who form an agreement to like and comment on eachothers posts when they come out to keep eachother at the top of the feed. these are far more formalised than what i find on tapas, and ive been wondering if something like that could be tried out on tapas...
the advantages of a 'pod' over simple informal mutual readership would be an open discussion of what we can do for eachother, a collective organisation rather than 1:1 relationships, and an agreement to not only engage with eachothers comics but also do this as a group and in a timely manner. it could be a good way for a group of small, up-and-coming creators to band together to work the algorithm.