I agree that having to introduce a convention is not ideal. Though I’m considering trying it.
My first approach to this was trying to get my editor to do some sort of overlay (and not need any special comment addition) to make the TEST line stand out, but I’d need to do some research to get it to work (if even possible), like:
Actually, I think a § (section sign) or ¶ (pilcrow) is a better/good symbol than the triangle.