via is a commonly used label to note through what or whom content was first discovered. E.g. if A posts a photo, B publishes a post mentioning (or liking or reposting) it, which C sees, C might post something like "Look at this cool photo by A! (via B)", where B can either be linked to B's profile or the specific post they saw. Sometimes, this can form a long path until the actual source is reached.
Very interesting paper from UC @berkeley_ai examines the innate knowledge that helps humans solve computer games more quickly than a RL algorithm: https://arxiv.org/abs/1802.10217 via https://www.technologyreview.com/s/610434/why-humans-learn-faster-than-ai-for-now/
- give credit (especially if found via a longer piece, not just a simple like)
- social discovery: people seeing this and liking it might want to follow B
- documentation for yourself
- in-between post might have additional information readers might be interested in, but you want to primarily credit the original
no known examples explicitly marking this up. A potential consuming use-case could be recommendation tools (see 2. above)
- Sven Knebel: I sometimes wish Twitter would document when/why I followed someone. I could post follows that reference through which other post I discovered someone/decided they might be interesting enough to follow.