I checked some other ideas that came to my mind. Contacts isn't cloning themselves only. When I reboot the device without disconnecting the chat app, or just after crash, then after reboot I will get every one contact cloned. It looks like it's remembering the contacts, but after reconnecting when something went wrong it's downloading them again and loads the list that is already saved resulting in cloned contacts.

For a meantime I just built another group with "most used" contacts. I can chat and everything seems to work.

I don't have enough knowledge to find the real reason for this bug so I will go the easiest way. It's looks simple, find out where contact list is saved, then make a script that will delete list before my account goes online, result? It still should download list from server, but will have nothing to load from memory so the contacts wouldn't be cloned, I think. Of course if my way of thinking is right.

And to your last question. Im running Diablo Turbo OS from flash memory, In my opinion is efficient enough and waaaay faster than it was on nokia 770.

Never even tried booting from SD, just did it with my 770, but for n800 I see no reason, but, now, as you mentioned it, it will improve not-bad-at-all performance on n800?

The only thing im using internal card for is for swap with swappiness around 30 and it seems to work just fine, as I like to have few apps open, be multitasking

External card is for stuff and rubbish

Edit 1:

As far as I know N900 facebook chat is too connecting through jabber in the same way as the new Diablo-Turbo Plug-in for n800, but on n900 I never faced similar dilema, or and kind of problem with chat.