You're correct in a lot of what you say. The system was indeed designed for low-bandwidth systems using teleprinters, hence the upper case only business (The teleprinter alphabet is only a 5 bit code unlike the ASCII 8 bit code used for computers and does not include lower case characters). It's also a worldwide standard so it has to be able to cope with the comms available anywhere on the AFTN. I'm not an expert on the AFTN but certainly teleprinters were the standard until relatively recently.
The Q LIne is in a totally standardised format while the E line (that contains the text) is free-form. The Q line is designed for automated selection and sorting while the text field is not.
Sites like the AIS one and other briefing services use the Q line to select which NOTAM to display. Some of them also try to parse the text in the E line to display something other than the circle that would be generated by the Q line.
The Q Line appears in the AIS briefs at my behest, it wasn't there in the original implementation in 1992. The reasons for adding it were twofold:-
1. It enables you to answer the question "why the *&%$ is that in my brief?"
2. It enables people like drauk of fly.dsc.net to use the Q line to manipulate the data for alternative filters and selection criteria that are not available through the standard AIS interface.
There's no need for pilots to understand the Q line in order to understand the brief.
The actual format it is delivered in is an international standard. Like TAF & METAR the format is the same around the world so if you can understand what you're given whether your in Cosford Canberra or Calcutta.
Work is underway, led by Eurocontrol, with the support of the FAA on an xml interface for exchanging data, which will include the ability to exchange graphical data including charts and positioning information. It's called AIXM (Aeronautical Information Exchange Model) and a quick Google will bring up information. It is hoped that this will eventually be adopted as the ICAO standard, which will allow much better presentation of the data and automate the process of uploading it to FMS.
Mike