r exports in lr4 lossless?
From what I understand, whenever you convert, you lose, period (It has to with rounding or averaging). Starting with, and working with, the original (RAW) data is always best. At that stage, export to whatever format/color space/bit depth you please.
As for the OP'S context, if one word had to be given as the correct answer, then it will be yes.
Me, on the other hand, couldn't be bothered with worrying about. Go out and shoot and get your exposures and WB correct.
but if we are getting technical the OP asked about exporting from, not importing to LR. For that operation I think most would agree it is lossless.
Getting technical is why I say "Yes". From a non-technical perspective, then I would agree with you and that there is no VISUAL loss under further editing (providing extreme editing is never performed).
Bottom line - for the purpose of the OPs question, as long as they stay away from JPGs most people would consider it a lossless export.
Agreed, 99.999% of people would agree that it is lossless.
Only when you can criticize yourself, should you criticize others. Mikes.