Rob... Bob... Why y'all gotta do this to me so early in the morning? >.<
1) It's not publishing in the truest sense, they're more like an on demand printer.
2) The creator(s) retains all the rights. The right to publish it in the specific anthology is the only right that MR has with your permission.
3) Initially, the editorial process was supposed to be a pretty rough one but to keep the experience fun and light, we just kept it simple. Like Rob said, the creator is the one responsible for most of the editing. You can ask other members to review your work if needed.
4) You can get involved by drawing standalone art, drawing manga, or finding an artist to draw your manga. If the latter is the case, both the writer and artist get credit (Story Written By: Illustrated By:).
When getting involved, make note that it is important for the writer to be able to draw basic character sketches and panel layouts for the artist (Unless some other arrangement is agreed upon in the beginning of the partnership) so that the artist doesn't have to continue to redraw characters and scenes. This saves both writer and artist valuable time. Panels can be as simple as shapes and stick people with labels.
One last thing: If at any time a work needs to be removed from the anthology at a later date, it can be done but the printer charges a fee (currently $20) to make the appropriate changes to the print document.
If you have any other questions, I'll be glad to answer them.