Are loners or those who prefer their own company pitiable?

There's a difference between being lonely and being alone

No, not as long as it's their choice. People have a right to design their own lifestyle and their choices should be respected.

Besides, I'd far rather live next door to a recluse than Party Central.

All loners don't prefer their own company so those who do aren't pitiable

That they "prefer" it makes it not a pity.

Maybe, sometimes depends on the reason. If they prefer their own company out of fear, anger, or anxiety then maybe yes.