Bernie, I have been blocking Costa Rica on eBay and I just removed it on my website. Why? Because I looked at how many shipments we had to Costa Rica last 3 months and how many problems there was with this country. Many addresses have no street numbers, so out of 3 orders there I had a INR claim and shipment came back to me as undeliverable.
We are fairly popular in Brazil and Italy and have several repeat customers there. Italy used to be a problem, seems not anymore. Many sellers do not like shipping to Brazil.
Bernie, I am always polite in my responses, never sarcastic. The most outrageous response would be just a one sentence factual response without "Dear Xy" and "Best Regards". My response to "Please give me tracking number" was "Already did, please scroll down." while I was hitting the punching bag with other hand to release the frustration (metaphorically, I have no punching bag around, usually I just say "Dude, you must be kidding me !!!" and that kind of helps).