I made a compilation of Cloud Discontinuity  observed from ground based telescopes near the dates of BepiColombo flyby. 
Javier Peralta pointed me out a confirmation obs. by A.Cidadao. 
I made measurement of the wave speed between the 3 obs. as you can see on the image. A bright streak is following the dark wave. 
The Discontinuity is also visible in J.Camarena image of Oct.16 but is very faintly seen.

[Manos Kardasis,Glyfada-Athens;Greece]
《カーダシス マノス:ギリシャ アテネ》