I would also guess kind regards, but in 50 years of speaking and writing formal/informal/technical English I've never seen that one!

I notice in Skype groups that I've been involved with, I continuously see things such as-

u = you

wt = what

hand = have a nice day (I thought it was a body part, my mistake!)

k = okay

ruf = rough ( because the correct spelling is too hard and makes no sense, or so I was told)

thot = thought (not to be confused with the Norse God Thor)

picter = picture

and the list goes on! (Note: the last 3 aren't accidental mis-spellings. I was told directly this is a better way to spell these words because English spelling makes no sense and is too hard to remember).

I have had times where I had to ask people what they were trying to communicate and they are shocked that I don't know what they are trying to say.

It's a different world my friends, laziness is king! :)

The messaging culture certainly has not been kind on the language. As if gonna and wanna weren't bad enough, now we also have to contend with such laziness in formal emails. CU, LMK. BRB.

I would imagine KR stands for Kind Regards, but I have never seen the abbreviation used.

I have also seen BR for Best Regards.

When I saw "KR", I just read it as South Korea.