With the "hidden by interface" statement, I referred to aspects like dwarves who don't like helping people, but who have doctor experience, not actually helping dwarves, and generally leaving them to dehydrate to death. Many people who play just let whatever migrant that walks in with doctor experience be their doctors, watch these doctors (who for some perverse reason, seem unusually likely to dislike their patients, and don't treat them for people who supposedly have experience treating their patients) not actually do any sort of medicine on injured dwarves, leading to most of the deaths in the hospital.
Yes, maybe if more people knew that "likes helping people" is a required trait for doctors, this wouldn't be a problem, but the thing is, most people don't look for that. (That's what I was referring to in the quote at the time, as well.) Yes, traits are there, if you go through the unit list, and look at the detailed view of the dwarf, but it's buried behind several layers of interface to see what traits a given dwarf has, and players have little way of telling when one trait actually is having an impact on a dwarf's behavior, especially since so many traits appear to do nothing at all.
The way to solve this is to make it clear to the player that the dwarf is doing (or not doing) what they are doing because of a personality trait of that particular dwarf, and not something endemic in the coding of dwarf AI (which people already assume is why dwarves do stupid things). This means you need to put some sort of message to the player that says "Not working because this dwarf is lazy", or something reasonably similar.
This also means that if you are going to make personality traits major aspects of what jobs a dwarf will be useful for, then maybe you should put it in one of the more easily-referenced screens in the interface, and not hide it underneath the description of the curliness of their ear hairs or how stained their teeth are in the detailed description of creatures. Data that is important to determine how to use that dwarf should have an important place in the interface for easy reference. Skill levels, (being very important,) are put in a very easily referenced place when you are considering what labors to assign a dwarf. If certain traits are critical to doing certain jobs well, they should have a similar place in the interface.
Regarding military, as far as I can tell, most people just plain give up on using crossbows rather than deal with the still-lingering bugs in it. Yes, you can manually force a workaround with only assigning one type of bolt to them, or you can just do without them, but that doesn't mean it's not a problem that needs to be addressed.
With that said, reworking the military interface so that it wasn't such an obstacle for people to learn without losing any of its current functionality is both possible and would obviously be an improvement, although that wasn't what I was arguing in particular.
People play 40d and avoid playing the newer versions just because they look at the military screen and decide not to bother going through the effort to learn it. These are people who have played DF for years, and not just "casual players" who don't want to bother with any game that isn't very simple, these are players who have just grown tired of trying to get their heads around a fairly obtuse interface. (Which is, incidentally, the camp I think Phoenix20, here, lies in.)
Interface can be improved, and it can be improved without harming the functionality of the underlying systems. You can build a system to be easier or harder to learn, just by the way you lay out the buttons, even if that system is "complex on the level of building an automobile".
And on that note, seriously, I've written a major suggestion thread where, thanks to Toady talking about how much he would overhaul the farming system, "if he could find a way to properly display that information to the player", I have redesigned farming, ranching, herbalism, fishing, and wood cutting and built a mockup interface to show Toady expressly how this can be best displayed to the player in a reasonable manner, without using absolute number values, and without forcing the player to learn chemistry. The
mockup interface proposal is here, and if any part of that interface is confusing to you, then by all means comment in that thread so that I can address it. It's much easier to fix an interface when it's all hypothetical in a spreadsheet program than once it's actually implemented in the game, so I hope that we can have enough of a debate going that the interface will be refined enough that we can simply hand the interface mockup to Toady and say "here, make it like this".
edit: double ninja'd but whatever.
I did an experiment on the "creative" thing, by the way, because there were rumors of that going around. No personality trait I tested had any impact on what those dwarves engraved. Every dwarf (of 10 dwarves, with various personality traits both low and high and with no trait score) had virtually identical proportions of engraving "types". "The dwarves are travelling"-type engravings (I.E. foundation) appeared to have a 20% chance of being engraved, regardless of any other factor.