I can only speak for myself, but some kind of clear visual indication is needed. For example, when you are scrolling through the code, looking for a sub, it will make it much faster to find, as the brain won't have to process the code, just look for that indicator and the correct name.
However, if the editor won't support it, well, not much to do. But, in that case, a nice fallback would be my earlier suggestion: an option to change the background color on Sub lines. In fact, I would like that better than divider lines.