The ramping up/ramping down is part of how /fupdate works, ie. to react quickly to bursts of messages. I cannot add another level to that.
As you mentioned, with timer/play-based echoes, scrolling text appears more jerky because there is a continuous stream. For incoming messages, this is not as much of an issue, as messages often arrive intermittently.
That said, I could disable /fupdate for timer/play-based echoes/commands, so that they update windows immediately. This would allow us to set a /fupdate default which would only kick in during non-timer-based echoes, ie. message bursts.
