Regarding point 1, remember that there are no salary negotiations at Stack Overflow. No one gets a raise because they ask. People get raises because they demonstrate skills, increase experience, etc... A candidate will have an initial skill evaluation they might not like, but they are pretty much guaranteed to have a much better one after one year, and if it is a big positive correction, then be it! There are no negative corrections btw - previous years salaries are at least maintained.
Secondly, I sincerely doubt we'd make an offer to a candidate that assumes their skills are all at the top of the range. "Fives" are extraordinarily rare, most employees have no fives, and the ones that do have one five.
Regarding point 2, as an employee I am not concerned with the salary of others per se. I know that they have the salary which corresponds to their perceived skills. It's likely that I would object to some evaluations of skills if I saw them, but that's an order of magnitude healthier than having salary envy. In fact, keeping evaluations fair and in check is a very good thing for the company.