Told you my grammar knowledge is limited. 
I guess for me it’s how it is taught and that is mainly to conjugate from the dictionary form. This can even be shown in the SRS practice level in this situation:
It’s telling me to go from 遊ぶ to 遊びに行った.
To be honest I’m not sure there’s a right or wrong way to go about this. Personally, I would prefer for the dictionary form to be referenced and for all linked vocabulary (in all it’s forms) to be referenced in the context sentences.
I’d say to just be happy that you stumbled upon this way of making nouns. 
I can’t think of a lot of examples right now, but here’s a couple:
折る⇒折り紙 = “paper folding” origami
畳む⇒畳 = tatami mats
Hey now 
Is the こぞ on the landing page meant to be こそ?
So after a bit of experimenting I have found what seems to be the problem.
Firstly, no matter what the first sentence I review for a new session has all of the furigana each word. After that it is only words I have not clicked on or off. This is a minor frustration its almost like Bunpro only checks my furigana list after the first sentences.
Secondly is more a UX than a code issue and its that when you turn a furigana off for a particular word it originally would automatically go away. However, now with the hover feature when I click on it, if my mouse stays overtop of it, then the furigana will remain displayed with no indication that it been checked as understood.
Two naive solutions:
First and harder would be that there could some little feedback, an effect or sound or something that just recognizes the click has been inputed and registered. I am personally always for a bit more game feel but I don’t want to scope creep the UI right now.
Second would just to have the hover feature of turn on after you check the word and move your cursor off of the word. Then after re-hovering it would be shown. This would be trivially easy I imagine unless I am missing something obvious.
PS I maybe should make it clear that I do not use Wanikani for philosophical reasons, so I may be an edge case that prefers to manually register which 読み I know.
