Druchii.net

Hm, I wonder do there occur treacheries on bought sides?
Do ever after the Sundering, were any elves who came on Malekhit's side?

And if yes, do Druchii society is open for those who find out THE TRUTH?;)

... or rather those differences, changes are so deep there were no change-the-side cases?
Do Chaos worshiping High Elves can became Nagaroth citizens, do you think?;>

This has been discussed before, I believe, and I'll leave it to those who frequent this forum much more often than me to fully answer your question.

I will. however, mention that in 5th edition there was a campaign called "tears of Isha" a High Elf who turned to the Dark Elves for what he perceived as vengence against his brother. Kaldor Coraith, son of Melenar, lord of Coraith, and the eldest, was passed over for leadership of the house in favour of his brother, Calaidan. Where Kaldor was a great hunter and warrior who was moody and ill tempered, Calaidan studied with the Lore masters of the white tower, learning both from the Sword masters and the Lore Masters.

In revenge for not being chosen for the position of Lord of the tower, Kaldor actually defected to the dark elves. Malekith himself was said to have have granted him audience, and allow him to join the dark elves.

Long story short, there was a long series of battles, and Kaldor eventually was impaled on Calaidan's Sword.

As for Chaos Worship, the Temple of Khaine actively suppresses the worship of the Chaos Gods. Even though much of Dark Elf society had its origins in the worship of Slaanesh, Khainites rose as the dominant religious faction in Naggaroth. Chaos worship exists among the Dark Elves, but not openly. The most public affiliation between Dark Elves and the Chaos Gods probably has to do with the Convent, whose Sorceresses must naturally research and tap into Daemonic energy as part of their training and magical practices.