I am wondering... do you submit high quality sites to your own directories? Is this a way to increase the quality of your directories and does Google and other SE like this action?
Look at your directory from the standpoint of a visitor. If you were visiting a directory to find resources wouldn't you expect to find links to quality sites? There are also many other good reasons to add high quality sites to your own directory. To name just a few if the descriptions are unique you have just created more content. You affiliate yourself with those sites listed - if they are quality your directory is more likely to be perceived as quality and there are many more. I have yet to hear one really good and valid reason not to add quality resources to your own directory.
100% yes. Our database has been built on that methodology for the past 8 years. That's the one benefit of some of the better smaller directories, the content is clean and good. Not like some larger content ones who claim to have a lot of content but when you look at it they are cloned dmoz.
There are so many educational, science, government, etc sites whose administrators won't come to my directory and submit these sites. On other hand if I want to build good directory, I need quality sites, which my visitors will find interesting to visit. So I think it is OK and it is compulsory to add such sites to my own directories.