Can superficial veins with clots in them be safely stripped from the leg?

Depends: done for infection on occasion. Usually will shrink up or atrophy. On occasion will recanalize. In the clinical situation of varicose veins and some clotted branches " stripping" can be a useful tool.

Yes: If the clot is only in the superficial vein/s it is safe to remove the vein surgically with either a phlebectomy or stripping.

Superficial clots: Superficial veins with clots can be removed safely under local and tumescent anesthesia through micro incisions (microphlebectomies). This should be done by an experienced vein or vascular surgeon. The alternative to removal would be wet heat to the area and ibuprofen.