Rather than confuse the HdF thread with another D system being reviewed before the current one is done, I'm going to make a start reviewing PdL, starting with the M and D routes in Nantes/Loire-Atlantique. I'll get back to Aisne when Oise is activated.
M9, M11, M11Sor, M17, M26, M31, M37, M37A, M39, M39ChS, M39A - fine
M42, M49, M57, M57A, M58, M58Pel, M59, M64, M65, M68, M69, M69ChN - fine
M75 - remove D75 point (or merge with other M75 section and delete D75)
M75Cha, M76, M80, M81, M85, M89, M91, M101, M105 - fine
M107 - M107A -> QuaiEmiCor_W
M115, M119, M137, M149, M178, M178A, M209, M215, M264 - fine
M337 - signed as continuing to the river, as per OSM, so southern end needs changing
M358, M359, M617, M723, M751, M751A, M823, M965 - fine
add M417 (signed from N844 exit 30)
There might be a need to check GMSV to recheck the system. My checks of various routes on OSM that weren't in the browser were mostly just legacy D stuff that hasn't been removed but had no route signage. There were quite a lot of signs for M roads (using white, rather than cyan, backgrounds), but I did find some legacy D roads that hadn't been removed/changed. Other than the three issues listed above, I didn't find anything suggesting that this wasn't mapped properly, but that doesn't mean that you won't.