For the most part, I'd say it's non-linguists that drive innovation in language; or, as we hear so often in North America, it's "so not the linguists" that make things happen in the hood.
Example: Ronsard and Du Bellay attempted to shape the French language with their "Défense & Illustration de la Langue Francoyse", and they were the ones to succeed, if anyone could. No one paid attention, and their proposed innovations never caught on. Does the Académie Française do anything? Do we lose anything not having an English Academy? I think it's clear language is influenced very little by those who study it formally, as compared to those who merely use it.
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