I am not pulling your chain; let's consider your examples:
"What screws you use with that motor" or "pot direction mislabels": This kind of basic info should definitely be in docs and not relegated to comments. I believe you can find this level of answer in comments, but the answer existing there should not be considered a virtue: it's an indication of poor documentation in the first place.
"Why I fried that thing backwards" and "need any other product to hook that up to my IMU": This *is* general knowledge, and it's also not likely to be covered well in comments.
I am not convinced of the existence of this intersection of "misc info" that is not general knowledge yet specifically relevant to a product but also should not be in the docs. I think the forum does capture the misc info aspect; if your quest is for knowledge, why do you care if you're searching in product comments or in forums and official docs? Do you at least agree that having all the info in organized documentation is a better goal than having all the info in comments?
I don't understand your statements toward the end. How would comments have answers to "questions people will not spend time to ask" any more than any other format?
Disconnecting powered stepper motors is usually a bad idea, and we've added a notice to that effect on our driver pages. By the way, changing connections while power is applied is generally bad even when you're not talking about stepper motors.
I think your reduction of comments to "Knowledge" is the logical step I disagree with; the ideal is not borne in reality. There is no shortage of information out there, and combing through comments on product pages has to be one of the worse ways of acquiring knowledge. Datasheets, web sites, and books by people who know what they are doing will have a much higher density of the "quick lines from experts" you're looking for.
The quick answer is that the torque goes in a straight line from zero at the no-load speed to the stall torque at zero speed, so at around 10% of the stall torque, you can expect 90% of the no-load speed. So, without factoring in any other potential issues such as whether the voltage range is good for your application or if the motor is convenient to mount, the motor you mentioned should be fine the application you described.
I had not heard about the robotics merit badge, and we have not done anything to get ready specifically for it. I looked around a bit and didn't find any details about it; can you provide some specifics of what's involved or links for more information? What would you like to see us do in anticipation of this launch?