Rectangle shaped keyrunes
So I looked through a bunch of option and came to the conclusion that it is probably an issue with the glyphs themselves and not the css settings.

It seems that keyrunes assumes that a set symbol is roughly the size of a square. 
You can see that here: https://mtg.gamepedia.com/Set

While there are in general many square shaped set symbols the dimensions of a set symbol are more akin to a rectangle with double the width of the height. You can see that quite well on the promotional star: https://scryfall.com/card/j14/8/%7Cducgnorn-gsedzaonobt 

I wonder if there is some possibility to get rid of the whitespace on top and bottom on the more rectangle shaped keyrunes: ARN, ATQ, FEM, ALL, WTH, EXO, UGL, EXO, USG, ATH, ULG, BRB, NEM, BTD, LGN, MRD, EVG, SHM, M10, M11, M12, PC2, M13, V12, GTC, DGM, M14, M15, DDN, C14, FRF, TPR, V15, C15, W16, EMN, PCA, W17, UST, M19, MED, GRN, UMA, RNA, MH1, M20, UND, M21, 2XM, CC1, PMEI, PGRU, and I probably missed a few.

Or to put it differently I would like to have an option to set the height of the symbol and then have the symbol display at its actual height and not half its height. 

I am not sure if this is possible with the current setup. 
