It wouldn't make sense that muscles would be damaged through use. The anus is no different. The only note of caution is that any muscle can suffer from temporary strain, but that's easily fixed through rest and time to recover.
As you pointed out, he anus is no different from any other muscle in the body. It looses elasticity and strength if not used on a regular basis. I would agree, if there is acute pain or discomfort in a particular spot, such as occurs with a tear, that rest is required. However, the best thing for general muscle soreness is to continue to use the muscle. That's why i always recommend couples doing a month of anal only try to have sex at least three times a week during that time, even if she feels a little sore back there.
Even my wife can get a little sore from time to time when we've had a particularly long or vigorous session.