As always, that Sheldon Brown link says it all. There are very tangible differences in the rides of different frames, it's just that it doesn't come down to material, but to how the bike is designed. xrodolfox is right that what tires and at what pressure you ride them are important to comfort - but put those same wheels and tires on a different bike and you may have a different experience (my main three road bikes are carbon, steel, and ti and they are entirely different in their rides with the same wheels/tires). Dont worry about breaking the carbon. The main problem with any bike is usually the deraillure hanger and most carbon frames will have a replaceable one. You probably won't want to clamp something on to a carbon frame though, so keep that in mind for touring. Since comfort will be key for you, try and at least be able to do some riding on the frame you will buy and get properly fitted to it by a reputable shop. If you know somebody who can recommend a good local shop for fitting, go with that - a lot of shops are pretty clueless these days it seems. I can't quite get my head around what the quote from LG means. Parts are parts no matter what frame they are one. If they just mean the frame itself, then, yeah, if you damage a carbon frame, it is likely done, whereas a steel frame can often be bent back or a dent removed. Most people get years out of their carbon frames tho. I don't think there is any reason to stay away from carbon, but conversely, there's not necessarily any reason you should focus on it.
If you are looking for effectiveness you can certainly save some dollars on your components. bottom end (usually) = not so good, top end = very minor gains, somewhere in the middle usually gives the best bang for the buck.
Four touring your seat will be important! but that is a very personal thing.