Most of the things I miss revolve around the community features and how good LJ was for MEDIUM-SIZED conversations: You weren't stuck in your immediate circle but neither were you just shouting into the terrifying public void like you are on, for example, Instagram or Twitter.
There was very, very fine level of access control over who could see what which meant you could require CONTEXT to be a part of a group. In addition, tagging support was robust and NOT just a mixture of hashtags. So you could do things like, in a politics group, click 'Elections: 2004' and see, in chronological order, every post related to that topic in the group. This made actual search possible and cut down on reposts/recycled content, because things weren't just lost the minute they fell off the front page, etc.
I agree with Mezzie about the good things about LJ, but one thing I think he/she is wrong about is that Twitter is "shouting into a void." In fact, even though your tweets may be set to public and any user can read them, your followers are your "circle" and most interactions come from there, not from random people.
The difference is that the access controls were built in to LJ and they're an afterthought on Twitter. The ability to finely control VIEWERSHIP (multiple different friends groups, for example) dampened a lot of things being shared without context.
Then again, screenshot culture wasn't really a big thing, yet. I don't think we could replicate some of what made LJ work anymore. It's sad.
There was very, very fine level of access control over who could see what which meant you could require CONTEXT to be a part of a group. In addition, tagging support was robust and NOT just a mixture of hashtags. So you could do things like, in a politics group, click 'Elections: 2004' and see, in chronological order, every post related to that topic in the group. This made actual search possible and cut down on reposts/recycled content, because things weren't just lost the minute they fell off the front page, etc.