There's another approach that I like better:

HND-sin-HKG-PER-mel-bne-syd-lax-JFK-dfw-LHR-doh-NRT

That is, stops in ALL CAPS and transits in lower case. Why? you ask.

The very first thing I do whenever anyone asks for help with an itinerary is to copy their routing and paste it into the GCM. With this format it's completely simple. Having to edit their string in whatever way, e.g., deleting x and o and whatever other faff they've put in, can be a PITA and sometimes it even dissuades me from commenting. I mean, you want to make it as easy as possible for people to help you, right?