Turn %\% issue into an R bug report and then delete it

[MichaelChirico]

With many years of hindsight it's clear this is a bug:

https://stackoverflow.com/q/32748895/3576984

I still see 'unescaped bksl' in the tools/R/QC.R code, so this is probably still present.

Filing this as an earmark to remember to isolate the issue & file a patch for it.