This was seen both on Lithium and Beryllium.

During review of integration/test change, I have seen a contribution which had left bash-style comments in their JSON data, but Sandbox job was 100% passing. To remove possibility of Robot libraries doing some processing, I have created test Change 32890 [0]. From patch set 1-5, only #2 fails.

So it looks like (the JSON Java library used by) ODL removes such comments, which is not strict JSON behavior.
This is not necessarily a bad thing, but ODL wiki [1] should mention this functionality.
Or ODL should disable it, perhaps squeezing out some performance improvement.

[0] https://git.opendaylight.org/gerrit/32890
[1] https://wiki.opendaylight.org/view/OpenDaylight_Controller:MD-SAL:Restconf#Supported_data_formats