The actual research into welfare-maximizing tax systems argues for a UBI plus roughly U-shaped marginal tax rates, i.e. relatively high phaseout rates on the UBI itself, then low but mildly progressive rates for folks making more than the breakeven point. The point, I think, is that this strongly incents folks to become net contributors, since at that point they will be paying lower marginal rates. Your point about whether the UBI should be taxed is interesting. Of course at any given time it's a wash, but you might be right that taxing the UBI itself (say, depending on tax revenue as a fraction of GNP) is a good institutional choice.
You could just adjust the UBI payout to achieve precisely the same result? Or is there another variable being maximized there relating to, say, household size? (Or is it just psychological?)
This thread is for asking any questions that might seem obvious, tangential, silly or what-have-you. Don't be shy, everyone has holes in their knowledge, though the fewer and the smaller we can make them, the better.
Please be respectful of other people's admitting ignorance and don't mock them for it, as they're doing a noble thing.
To any future monthly posters of SQ threads, please remember to add the "stupid_questions" tag.