The old exporter would convert \\ at the end of a line to <br /> to force a line break. The manual still says that \\ will force a line break, but the new HTML exporter, while indeed breaking the line there, does not insert the <br /> to make it render as a new line.
This is using the latest version from Git. I think this is a bug, not a limitation of the new exporter. Best regards, Terry -- T.F. Torrey
