Factorio Forums

When you have a straight line of ghost pipes and place a pair of underground pipes directely above and below, the ghost pipe is deleted. This does happen for a single unconnected non-ghost pipe, too. But for a ghost pipe, it happens even if the ghost pipe should be connected to an assembler or another pipe (but ghost pipes dont have pipe connections, so it doesnt detect) on one or both sides.

Yea, it checks whether the pipe goes elswhere, which it doesn't check for ghost pipes.
I would like the ghost pipes to have the visual connection similarly as ghost belts do some day, which, as a bonus would allow reasonably easy implementation of the logic also for this case.
Until then, I would say that it is too much of a corner case to be worth to do it now, especially when it is only related to manual building and not blueprints, sorry.