I read about this months ago. I could have sworn it got patched out at some point, but I've experienced it twice in the last 3 days. AI demands I stop settling/buying tiles near them, I say I'll settle where I please or none of your business, etc. I get diplomacy hit. Later dialogue leader says they are disappointed in me that I broke my word and I get new diplo hit. By this time, the "old" diplo hits for honestly saying "I'm gonna do it anyway" have faded, so I guess the net effect is cosmetic, but a bit confusing and obviously buggy.