Re: Text editting
400 baud was an odd speed. The standard speeds were 75, 150, 300, 600, 1200, 2400, 4800 and 9600. Some terminals would do 19200, but that was generally frowned upon because of the interrupt load on the server. Faster speeds came about when people started running multiplexors or PPP for internet access.
But yes, that was one of the reason why vi commands were so terse, and the requirement for curses to optimise screen updates. Vi was written to be able to work over the slowest of lines with the most basic of terminals. All you needed was full-duplex communication, the alphanumeric keys and some punctuation. The terminal had to have some form of direct cursor addressing and at least a home and clear screen command, that could be encoded in termcap. But even the, there were some terminals that were just too brain-dead to be used for vi. I seem to remember some comments in ancient termcaps about a super-beehive terminal and maybe one of the Ann Arbour terminals.
What was most concerning was terminals that would not flow-control properly, so there was a mechanism for encoding timing delays into the functions so that curses would not overwhelm a terminal, preventing corrupted screens.