perhaps we should at one point revisit how we handle dragging with the mouse (and/or zooming). It might make sense to "snap" to more logical values while dragging and/or constraining zoom levels so that the coordinates don't get too weird.
Now I increased the preference "Numeric precision" to value 10 and everything is in most cases OK even if I move the path using the mouse: only the first pair of coorditnates has 10 ciphers, whereas all the following relative coordinates remains integer pixels. But the coordinates *.000001 or *.999999 still occur (even if the coordinates remain relative) if some part of the path is moved outside the left or top edge of the page, although the origin of the layer is translated to (-1000 -1000). But otherwise the workaround with forcing relative coordinates by translating the layer now works fine. (BTW, the entry "Numeric precision" has a misleading tooltip "How many digits to write after the decimal dot", whereas the value evidetly means the total number of valid digits.)