It seems like most of the covered_* tags are those where the outline of the object being covered is visible, e.g. covered navel. However, most/all of the covered mouth tags seem to be covering mouth instead. The same ambiguity seems to hold true for covered face <==> covering face, covered eyes <=> covering eyes, amongst a few other lesser-populated tags.

Can we standardize what covered versus covering means? For myself at least, covered should be by an inactive agent such as an article of clothing or accessory, whereas covering should be by an active agent such as a body part or something held. Thoughts?

The way I've been using it is covered mouth for when the mouth is simply hidden behind something and covering mouth for when someone is covering the mouth more directly, for example as a reaction to something surprising.

Unbreakable said:

The way I've been using it is covered mouth for when the mouth is simply hidden behind something and covering mouth for when someone is covering the mouth more directly, for example as a reaction to something surprising.

Pretty much the same.

Maybe its a present vs past tense thing. Covering mouth is like "in the act or just been acted of covering the mouth", while covered mouth is like "an object has covered the mouth for quite some time".

Admittedly I have no idea how they would work in single pictures per se. The only real difference I can tell is whether someone has like a scarf over their mouth vs someone covering their mouth to hide a laugh or something.