so I logged into one account and a couple old characters appeared. No big deal right? at first I thought I was rollin but then I started doubting myself as to how they got there and realized I deleted them like 2 YEARS AGO!! well that's weird! but it's like even weirder I logged into the character and items I had either traded, sold, transferred to other characters were there!

Anyone experience dis?

Yup.

well that's a little vague did you clash test any items?

Server migration. Old character database was stupid so some old characters resurfaced. Just delete them.

well yes but this character had some awesome stuff on him lol so I don't want to delete him! I'm just wondering what's gonna happen to some of the items

Same story here.
I've just read your topic, and checked some old accounts. Long ago deleted chars just respawned, with all items.
Are they safe to be used ?

It’ll create dupes and unperms if other copies of their items are floating around.

your versions of the items will clash and poof other versions. or vice versa. if you dont delete them the items you sold and now have will now be unperm. untill one version poofs

Does that include non magic items (like 15ed 3sockets Archon plate) ?

And may I ask... what about jewels (or runes) that would be inserted in the meantime ?

the non magic items is still duped
if the runes/jewels have been inserted in other items - the new ones would be safe to keep afaik