well, Turkey red lines were the only ones that were indeed red. Erdogan said that Turkey will not alow PKK from the north to join with Afrin. And lo and behold, Euphrat Shield heppen. Warned them about Afrin... and that to heppen. I dont see why Idlib red line would be dirfferente. Also, let not forget the shooting down the russian jet who violated Turkish airspace, on purpose, Turkey then also issued the final warning, and acted on it day after.
To cite again one high ranking US military offical: You dont want to **** with the Turks.ž
Im not conviced that Russia has such cloud to deter regime and iranian militias from at least trying to go for Idlib.