EO> "next" through each message.  I used BBSes quite a bit in the 90s,
 EO> though I don't remember if most BBS packages worked like that; however,
 EO> Synchronet's

It is pretty much the standard way to read messages, used by just about every
BBS not just Synchronet.  I think Mystic and one called WME were the only
software I ever saw back in the 90s that provided an alternative to the
traditional message reading, like you're describing.

There were hardware and bandwidth limitations that made it much trickier to do
back then, but I also think people creating these interfaces maybe just didn't
have the vision to make something different either.

--- Mystic BBS v1.12 A14 (Windows)