Question has come up a few times. Response is yes, non game breaking mods are allowed. If you're concerned they may upset the balance of the game, or get you in trouble, i would encourage you to stop use of the mod, send a ticket to the staff with details about the mod, and ask whether they believe it's okay to use. I have only seen one such mod myself so far, that fall in this category though.
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Discord: Tonkatunk#7079
https://github.com/Tonkatunk/Mabi-Pro-Lazyfae-Mods