HISTFILE vs. two or more bashes

[Dan Jacobson]

The HISTORY section on the man page should mention the case where one
has one bash session in one window, and another in another, etc., both
with all the same history related environment variables, including
$HISTFILE, inherited from a parent shell.

Is it only the shell that exits last the one who get to effectively
save its history, overwriting that of the earlier exiting shell?

Will setting histappend allow one to merge the two? Say if this is the
case.

Also where the man page mentions truncating the HISTFILE, one thinks
of the bottom of the file getting truncated, when it is in fact the
top. Mention this.