On the Eastbound island, I've seen a lot of regular commuters watch for the signal changing to decide what train to get on. I suppose this information will now be on the DMIs. But I guess also, you could watch for the while lights above the train doors.
Not only regular commuters! As a very occasional user of Earls Court, I've instinctively kept an eye on the signal colour if there were two trains platformed at the same time which were leaving in the same direction (even if it wasn't the direction I was going in, just out of interest). This (simultaneous services on adjacent platforms) is quite common for trains heading east to Gloucester Road etc, but only occasionally happens with two trains going towards High St Ken (presumably when an Olympia to High St is in at the same time as a Wimbledon to Edgware Road, when the Olympia shuttle is running).
So - a question. The old "first train out" sign, above the historic indicator (as discussed above) did, I think, only inform you about which of two eastbounds to board, and didn't do the same thing with two parallel trains both turning north. Will that be the same with the "first train" information on the new dot matrix signs? Any reason why the new technology can't do the same for both routes? (Though I hope it doesn't show the "first train out" all the time, even when the next trains on the indicator [or at the platform] are for
different directions; that would probably be confusing for unwary visitors, who might just think that information took precedence over the exact destination - if they weren't going far - and head to the "first train" when it isn't going their way.)