Here are 3 things where they require moderation & consistency:
Excessive effects
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Extreme use of reverb, echo delay, or other effects can limit the utility of a track. They should be used in moderation, or in a way that keeps the mix sounding balanced.
Panning balance
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Strong shifts in panning are not recommended. Especially in the low end.
Volume levels
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Volume levels should be consistent throughout the track. Sudden spikes or drops will significantly limit the utility for most projects. Also, it’s always a good idea to compare your levels with other content online, to ensure your submission isn’t too loud or too quiet.
Finally, while it is important to have consistent volume levels, it’s important to not compress tracks so much that they lose their dynamic range, this is particularly applicable to orchestral music, where retaining dynamic range is important.
You might want to read this very helpful article for your future submissions.