regression: piped less swallows keystrokes meant for next shell command

[Fry-kun]

With earlier versions of less (e.g. 608):

$ echo -e "hello $(sleep 2) world" | less -FRX
# <type in "ls" as next command before the prompt comes back>
hello  world
$ ls<cursor>

With version 643:

$ echo -e "hello $(sleep 2) world" | less -FRX
# <type in "ls" as next command before the prompt comes back>
hello  world
$ <cursor>

Many users type in the next command while waiting for the previous one to complete. This is especially painful when using source control commands which paginate most of their output. The current workaround is to turn off paging by default.