"Wow! I thought that there was no problem with checked fuel bottles and stoves, as long a they were empty and open. It is hard to believe that no backpacker who flies anywhere takes a stove with them."
There's a huge difference between the rules on the books and enforcement, IMO. I had to throw a used fuel bottle in the trash under the watchful eye of a United Airlines ticket agent in Reno about 10 years ago. On the other hand, I have never had any trouble carrying a used stove in my checked luggage, even when there was a TSA notice of inspection slip in my bag on the other end of my flight. I tend to agree with Justin Taul's assessment of TSA types as undertrained, if not necessarily idiots. Not to mention understaffed for the volume of luggage being checked.
" As to poles — I understand they can be checked in a tube. There isn't any problem checking them in a suitcase or duffel bag instead, if you wish to, is there?"
I have checked my poles dozens of times in a duffel bag, both in a tube and wrapped in a GG Thinlite pad bungeed to the side of my pack. No problems so far, even when I found the little TSA inspection slip. I don't see why a suitcase would be any different. I think the reason they won't let you carry them on is a concern that they could be used as a weapon.