What are the guide lines for philosophical questions to be on topic on this site?
A simple rule for philosophical questions would be along the lines of: "How does (this philosophy) shape current techniques, strategies, practices, or symbolism in this art/lineage?" which is emphatically not the same as an out and out philosophical question.
So, you might ask, "How does Buddhism shape this particular style?" which is not the same as "Would throwing a knee at an opponent at this point be a form of attachment and contrary to the teachings of Buddha?" The former is something you can easily point to the philosophy's own records along with historical records to reference, the latter is effectively a religious/philosophical debate.
If we want to nail this down tight, we probably should look back through every chi/ki-based question that gets shut down as poor vs. good questions and think about what the dividing line is in terms of both "evidence you can point to" and "questions we'd like to have on this site" as an excellent parallel.