Tro, I doubt this will do any good, but I feel a moral obligation to try. You regularly answer tax questions stating that if a married-but-separated couple hasn't spent a single 'nite' together during the last six months of the year, they can file as single. For federal income tax purposes, this is simply not the case. In some very specific circumstances one might be able to file as head of household, but unless there is a legal separation with a decree of separate maintenance neither person in the couple can file as single. Without the separate maintenance decree, the ONLY possible filing statuses are MFJ, MFS, or HOH. Filing as single simply is not an option. Please review Pub. 17, chapter 2. The sub-section on filing as single is only three short paragraphs.
There, I tried.