A reader writes to ask:

I am a bit confused about scene changes. I know that they have to be denoted by a single line with a "#", but if I use them at every scene change my plot will "unglue" a bit. There is something a bit Proustian to the flow of my novel that I don't want to interrupt, and the only breaks that I want are those between chapters. For example, suppose the protagonist is writing about his home. Then he starts to reminisce about another era, when he lived in a much poorer home in another country. From everything I have read online, it seems I'd better note this scene break between his actual home and his subsequent reminiscence of the old residence; but I feel something of quality will be compromised if I do it. Should I do as I wish with little fear of making some agent raise his eyes towards heaven, or should I be punctilious and proper and leave a blank line with the # at every line change, irrespective of how I feel about it?

You are under no obligation to indicate a flashback or other shift in time or space with a scene break. A scene break is simply one of many stylistic tools you can use to make such an indication. If you feel that an uninterrupted flow is best for the effect you want to achieve, then that is perfectly fine. If you do your job properly, then the reader should have no trouble following the change whether or not you call attention to it with a skipped line.