Sie feiert immer noch. Sie feiert noch.
In sentences like this, does the "immer" bring anything to the party ?
If they both mean the same thing, which form sounds most natural?
They both mean "She is still partying/celebrating." However, there is a subtle difference, in my opinion.
To me, Sie feiert noch is merely a sterile, factual statement that "she is still partying."
In contrast, Sie feiert immer noch has more of a meaning akin to "Can you believe it? She's still partying!" The speaker is subtly expressing surprise and amazement that the partying has gone on this long and still continues.
In merely written form, these two sentences are virtually identical. In conversation, however, it's the tone of the speaker's voice that would indicate whether the speaker is merely giving information or whether the speaker is amazed and incredulous that the woman is still partying.