In the Horner-Edition of the Southern Coptic NT-text (1921) Mk 15:31 has the English translation: „But likewise the chiefpriests also were mocking at him with the scribes, saying to one another, Others he delivered, but he, he is not about to be able to deliver himself”.
The ECM-Mark-edition has no Greek witness for „at him” and „but he”.
As I am doing research to reconstruct the Greek text underlying the Gothic translation and as the Gotic text is almost exactly the same as the text of Horner‘s translation. The reconstructed Greek text (< Gothic) would be: „ομοιως και οι αρχιερεις {εμπαιζοντες | ενπαιζοντες} [αυτω | αυτον] {προς αλληλους | εις αλληλους | μετ’ αλληλων} μετα των γραμματεων ελεγον αλλους εσωσεν εαυτον [δε] ου δυναται σωσαι.“
Since I don‘t know any coptic, I would like to know, whether the coptic sahidic text indeed has these variants.