Quiz: Remember the definition of mal de mer?
(From Usenet, GEnie, CompuServe) A more or less continuous chain of postings on a single subject, sent to a forum such as a Usenet newsgroup. To "follow a thread" is to read a series of postings sharing a common subject.
On Usenet these are connected by "Reference" headers. The better newsreaders can present news in thread order automatically.