I'm not sure if this has been discussed before, but to me it seems like something people should decide and use as a possible guideline.
Should one Element have both an effect and its "counter" in it?
Note: by effect I mean a card or creature ability mechanic
So, for example, Quintessence. Should Aether have a counter to it? Something that could get rid of the immaterial status? Should it be in a different element? In chat, Higs mentioned that an anti-quint couldn't be in Time, since they can't really affect each other. That makes sense, so another question to answer could be "Should an effect's counter be in its opposite element?"
Basically, just post what you think about having an effect and a counter to it in the same element. Do you think it would make it OP? Would it be ok? Would the element seem more than complete? Why?
I hope to come to a conclusion, so other people could look at this and say, "I shouldn't post a card idea for an Aether card that would be an anti-quint." Of course it shouldn't become a formal rule, just a display of the community's opinion.