I know things... A lot of things.
Join Date: Feb 2015
Motorcycle: GSXR 750 K4
Re: suspension/setup advise
It's true these bikes weren't designed for comfort, in that comfort in itself wasn't a main objective, but they were designed to be precisely controllable and there's so much precision you can have, if you're barely hanging on, all cramped up, with your extremities at unnatural angles. Ergonomics is therefore important and so, by extension, I don't think they were designed to be uncomfortable either.
Ergonomics, (which is one way of defining comfort,) depends on the rider as much as it depends on the bike though. Perhaps a bigger difference, with respect to "comfortable" bikes, is that they weren't designed to be intuitively ergonomic, meaning that you can't expect to just jump on them and feel right at home, based on your experience of sitting on chairs and couches. You have to adapt to the machine in ways that may not be immediately obvious. I've been riding my current bike for more than 5 years now, but after swapping it for a touring bike for a month or so, and getting back on it, the sitting position felt so weird, that I was actually a bit nervous while riding it home. I had to ride it for a couple of days, until my body (meaning my brain really) adapted and I felt right at home once more. For a rider new to this type of machine, it's naturally going to take longer than that (and it might never happen, if adapting to the machine isn't actively pursued).
As a more concrete example, I haven't seen a rider, new to supersports, ride one for more than a day, for the first time and not getting sore wrists. I also don't remember anyone, not attributing it to the "uncomfortable" (which really means "uncomfortable-looking, based on past experience of what comfort looks like") sitting arrangement. But sore wrists are a sign that you're supporting your weight on the grips, which are there for control, not support and the upshot is that you'll need to support your weight otherwise. Your core muscles are a large part of the solution, so there'll be some discomfort there, but even if the body position were more upright, you'd have to support all of you upper body weight through your lower back, so the discomfort would merely migrate there. (By way of illustration, try sitting on a backless chair for half an hour.)
In the end, I'm not sure whether most bikes can be comfortable, at least not if the word isn't taken too seriously. They can be ergonomic though.