Tildes is much like Hacker News and Reddit in that article previews are limited to just headlines. (Well, there are tags, but they're de-emphasized since they're hidden by default.)
While they are very concise, a problem with headlines is that we rely on them too much. Even good ones don't really tell you what the article is about. In cases where it's hard to read the article (because it's paywalled or whatever) the conversation can be based mostly on the headline rather than the substance of the article. On Hacker News there are often mini-disputes about whether the headline is clickbait or not, and what's a better headline. "Headline is misleading" is a pretty common complaint.
I'm wondering if we could add a bit more information? One possibility would be a "Subtitle" field. Lots of articles have subtitles that are somewhat more informative, and doing a copy-paste is pretty easy.
Another would be to have a "pull quote" field. This requires a bit of editorial judgement by the submitter about what's the best pull quote, but I think that's okay. It's still copy-paste so at least they don't have to summarize anything in their own words.
For the last few days I've been posting a pull quote as the first comment whenever I post an article, and I think it works fairly well, except that the summary says "1 comment" when actually nobody commented - it's just the pull quote. Also, having an explicit field for the pull quote might allow better UI possibilities, like you could put them under the headline in the topic list.