Enchantments seem to take up a slot in socketed weapons

[Adalon]

I'm not sure if this is intentional or not, but it seems to be a bug. If you do the enchant first, then you can only socket two runes instead of three.

[Cornflower]

I might add that in the one test I did, I added a Legendary Enchantment Stone to a fully socketed melee weapon. The Enchantment Stone over-wrote all the sockets, so I basically gained a few points here and there, but I didn't get three sockets and three rolls from the Enchantment stone. (Which would have risked creating a non-usuable weapon at lvl 43 or something, but on the other hand could have given uber-damage...)

[driller]

Enchantment stones will no longer be allowed to work on Socketed items.