I previously trained and managed a small team of UX writers and continue to mentor pretty much anybody who asks for help.
During our sessions we just about cover everything: micro copy, tone, passive vs active, capitalisation, hierarchy, working in teams, explaining our thinking, even mental health. UX writing has some big ideas, but the little things count just as much.
One common theme that comes up is where the UX writer belongs in a team, and where UX copy should sit in a workflow. While we partly depend on the organisation we work in, I constantly try to help writers understand that they must consider themselves as a core team member, and that UX copy is a core deliverable.