A single piece of non-public information that would move the market. Trading on that information is insider trading. Think "we have undisclosed losses equal to 5 times annual earnings" that your brother told you at a bbq. That is insider trading.
Inferring the existence of some information based on many other pieces of information isn't just legal, it is encouraged. "These guys must have some big undisclosed losses, remember how Mary used to talk about engineering projects and how she talks at BBQs now? Bob was saying his HR dept. is insanely busy. Ahmed resigned and took a job that looks like a step down for him. Ok I'm a sell on this." That is equity research and to be encouraged.
We could be interpreting this document differently [1], but keeping track of public forum postings by people claiming to work at tech companies seems quite far from a reasonable definition of illegal insider trading.
