I have seen both on lined boards, but probably more "in-between" than "on" -- though I have a lined, Moses graphite neck that's been sitting around for years, waiting for a project, with the dots right at the line/note (lines are hard to see in this photo, but they're there)...
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An on unlined board, I very strongly prefer the dots at the note. On a lined board, I can see the rationale for either (I might still prefer them on the lines, but not sure -- might depend on the execution and the specific 'board).
Re. other comments made throughout the thread, I am all for each player doing and using what works best for them on fretless. Lines, no lines, bright lines, dark lines, half lines, dots where you want 'em, even no dots. (Shortly after I put together the fretless Franken-Squier in my avatar -- my first fretless and still the one I have the most time on -- I tried blacking out the dots with a Sharpie. Maybe I'll give that a shot again, sometime, just to see what it does or doesn't do for me now. I'd be interested to see the folks @BurningSkies mentions, who play a totally blank fanned-fretless.)
The idea, though, that the only reason to go with a "blank plank" is out of some immature need to impress others, I don't get. Maybe it makes "no functional sense" for a specific player, but that doesn't mean that that's the case for everyone.
On the whole, I am a better (not amazing, but better) fretless player -- more accurate, more relaxed, more confident and more focused on the music -- without fretlines than I am with. There are situations in which I find lines helpful and ways in which I find them distracting and disorienting. I could elaborate on this and why I think it's the case (and maybe I will at some point), but the point is that, on the whole, unlined has worked better for me so far.
I can absolutely see that others would have different experiences and am not saying I'd never play a lined board (especially if I do something with that neck I've got) or that I'll never change my mind (or use some other sort of marking system that works better for me -- maybe some differentiation between the lines at different points -- I recently got a fretless fiver with tiny hash-marks on the side of the neck and am getting acquainted with it) and am not saying others have to do what I do. Whatever works best for you.