We are language learners or, at least, so does the title of the site says. But are questions related to the other side of the process also accepted?
It could be parents trying to teach their kids, teacher trying to improve their techniques, etc.
Learning and teaching are two sides of the same coin. Unless you're learning alone, how you learn is how the teacher teaches. Even if you're learning alone, the material is made by teachers (in a broad sense).
A question and answer site lives by the experts who provide answers on a topic that they know well. When it comes to language learning, the experts are language teachers.
Questions about teaching are very much welcome. (That's question about teaching languages — if you can replace “I teach language X” by “I teach biology” in the question, it's probably off-topic.)
For every "learner," there is a teacher.
"Teaching" is therefore an integral part of the language learning process. If you "teach," you're helping someone else learn. That's good enough for the site.