I personally believe, in much the same way that hushed whispers and steadfast belief can birth spirits and even gods with will and abilities far beyond mortal ken in the world of Gensokyo, not only are all ships with Marisa Kirisame canon, and not only are they all canon simultaneously, but also that all it takes is merely to speak one into existence, and it becomes real.
The simple and obvious reality is, no matter how strange or illogical, Marisa almost certainly is already dating (as a random example) Momoyo Himemushi, who lives in cave & eats over 10,000 rocks each day. Somehow. She's just like that. And because it's already true, we don't get a say in the matter, we just get to think about how cute, toxic, or catastrophically fucking funny it probably is.
