MetaTalk was the first subsite to MetaFilter, and started way back in March of 2000. The space is dedicated to letting members discuss any issues specific to the site itself. That includes things like policy discussions, asking users how they use the site, and also functions as a place to post feature requests or uncover bugs that need to be fixed. Posts to the site are sent to a queue for approval and the Frequently Asked Questions page offers a lot of additional information about MetaTalk.
If you'd like to know more about the MetaFilter Universe, read the about page for MetaFilter.