if you make a stalactite that has a length of over 64 (from what i've seen), then break the block supporting it, it doesn't fall, then, breaking the pointed dripstone second from the top will cause the one above to break off, supposedly, but if the stalactite is still more than 64 blocks, the top most pointed dripstone will drop itself, but be instantly replaced, thus duplicating it
Hey there!
This looks to be a duplicate of MC-206613.