“left;none” makes no sense, unless “none” is always understood as “through with no markings”. I’ve created a proposal for a new type of from-via-to relation that would solve this problem of lane markings not matching actual lane connectivity, as well as a ton of other issues with turn:lanes.

osm.wiki/Proposed_features/Connectivity

A connectivity relation could be used at that location to state how the lanes connect that would override the “turn:lanes”, allowing that tag to only state the lane markings, not the connectivity. If anyone has any suggestions for how to improve the proposal, please let me know!

https://github.com/osmlab/editor-layer-index