On LDOCE, at the definition page of "neither", there is one definition that describes the word as a conjunction, with the sentence:

The authorities were not sympathetic to the students’ demands, neither would they tolerate any disruption.

Is the usage of the word after a comma as a conjunction by itself as in the sentence really grammatical? If so, how often is "neither" used like this? Is "neither" used like this in America as often as in United Kingdom?

Thank you in advance!