I would say that so long as you aren't given any physical advantage that makes it unfair for other players (Like it's harder to kill you, or you can damage other players in unfair ways, etc.) that it should be fine. I mean, Optifine makes the game run much faster for some people, increasing smoothness of gameplay, and that's fine. It's an advantage for many people yet it's allowed. I don't see much wrong with a Status Effects mod, unless of course it shows you OTHER peoples' conditions. That would be unfair, and not allowed