Hi Stas and wikidatans,

the coordinates with (sub)millimeter precision might be imported from external dataset. With precise geodesic measurements, it is technically possible to reach such precision, yet it often decrease significantly by transformation to WGS84. Some places like important peaks or astronomy observatories can be located with such precision.

So I am generally against limiting the number of digits too much, but limit it to something like millimeter precision sounds reasonable.