is the winter leaderboard bugged? i can't see my position and my name in the leaderboard. is anyone having the same issue?

It works fine as far as I can tell. Just opt in and allow some time for it to register your XP, maybe refresh your browser.

Also, purchasing Civilisation package gives you +0 XP?..

i already opted in for the leaderboard. i just can't see myself in the leaderboard. in the autumn sale everything worked fine, but i think there's some bug here

If you bought it before the sale started, yes. I waited until the sale and got my XP.
Just contact support for a refund and buy it again (if you indeed bought it before the sale started, or just ask for your XP if not), that worked for me a few sales ago with Homeworld.

If you're talking about the display of your own name at the bottom, regardless of your ranking, then I believe it's the same for everyone. Currently, you won't see your name if you're not in the top ten. That might be working as intended or maybe your own rank will only show up later onwards, after some time has passed in the sale.

Sorry, I'm stuck somewhere around noticing the Pope dropped another four boxes of ziti. Everything else is a meaningless blur.