I agree that 'usage of English' sounds wrong. I think that in its linguistic sense 'usage' is normally qualified by an adjective, as in 'Fowler's English Usage.' But if it means employment of or consumption of something, it usually takes 'of' with a noun, e.g. 'The usage of postage stamps has declined.'

In this context, 'use of English' doesn't sound right to me either. It would suggest that the thread is about e.g. 'the use of English' on the internet or by the institutions of the EU.

But I think it was Admin who actually started this thread (to avoid pedants like me seeking to hi-jack serious discussions by making nit-picking linguistic points all the time) and gave it its title...