"Thou hast cleft my heart in twain"

"Thou hast cleft my heart in twain" says Gertrude to Hamlet. 'Cleft' is from 'cleave' meaning divide or split. Yet, I often meet constructions such as 'clefts' 'clefted' or 'clefting' in the writings of English native speakers. Has 'cleft' shifted to an infinitive in the modern usage? Or is it likely to? Believe it or not I've also encountered this construction in a newspaper: 'He clefts my heart in twain'. As a nonnative speaker of English I find this confusing.

Anyone to shed some light?

In linguistics, there is a construction called a cleft sentence (e.g., It is grammar that is at question.) The transformation between the more standard structure and this is called clefting, which I believe is a back formation. Outside that, I would guess it's an error. I can't find examples of verb clefts in the Corpus of Current American English and of the two examples of clefted, one looks like it might be a specialized medical usage.

One problem with cleave is that it has these two different irregular past tense and past participle forms: cleft/clove and cleft/cloven. Another is that it means its own opposite (both to split and to join).