Orthography or grammar?

The early Russian redaction of Kormchaya is a compilation of the Serbian and Old Slavonic
redactions of the Kormchaya book. It was created in Kiev under Metropolitan Cyril
during the last years of his activity, 1273–1280. There are several stages in the history of the
text, each associated with a certain region of East Slavic territory. At all stages, changes were
introduced into the text, first by the compilers of the Russian Kormchaya and then by the
scribes of protographs of the textual groups. At the same time all manuscripts retain the original
grammatical and lexical variants.
Novgorodskaya kormchaya of 1282 has combinations of words that are outwardly similar
to constructions with nominative direct object (kosit’ / kosili trava). These forms are found in
those parts of the text that were borrowed into the Russian Kormchaya from the Serbian redaction.
They reflect the Middle Bulgarian orthography of a copy of the Serbian redaction
used by the compilers of the Russian compilation.