This is something I’ve been grappling with a lot lately. My concern with “microcopy” is that humans have a tendency to ignore or de-prioritize things they consider small. To many micro = not important. It’s already a hard sell to get tech companies, particularly startups, to prioritize content without highlighting the small stature of this particular kind of text.
I don’t have a much better suggestion and I vacillate between different terms. I tend to call myself a product or UI content strategy and also talk a lot about interface or interaction content. Content Designer has never felt quite right to me either.
Thanks for your smart thoughts here.