This will send the commands at the same time to the server, so there is no lag time the target user can take advantage of to come back before the ban is placed.
I can't speak for all IRC Servers on this one.
But at least with IRCu and probably many many others (if not all), will read messages from a client into a received queue.
Then parse them when it gets the chance. It may or may not parse the two messages right next to each other, it may parse a join from the kicked client between the two, (perhaps via another server).
If the server is throttling your messages then it may just parse one line every two seconds or so. Which is more than enough time to let the kicked client back in the channel before the ban is set.
Just thought I'd point that out.
I've seen people rely on that so many times and wonder why it breaks.
