What do these warning/restriction codes in air tickets mean?

This is more a "related information" post than an answer per se, but it seems potentially useful enough for those interested in digging to be worth posting as an answer:

There is a wealth of information here - Travelocity - FARE RULES - not explanatory per se, but notes on fare rules written for use (it seems) by somebody familiar with the "jargon" involved. A number of extra codes are mentioned. Gives insight into practices, traps, ... .

This is specific to one route - see below. But other material may be turned up by searching, based on the page's content. They say:

• RULE APPLICATION AND OTHER CONDITIONS NOTE - THE FOLLOWING TEXT IS INFORMATIONAL AND NOT VALIDATED FOR AUTOPRICING. TRANSATLANTIC ROUNDTRIP STRUCTURE FARES FROM AREA 1 TO AREA 2/3. APPLICATION AREA THESE FARES APPLY FROM AREA 1 TO AREA 2/AREA 3. CLASS OF SERVICE THESE FARES APPLY FOR ECONOMY CLASS SERVICE. CAPACITY LIMITATIONS THE CARRIER SHALL LIMIT THE NUMBER OF PASSENGERS CARRIED ON ANY ONE FLIGHT AT FARES GOVERNED BY THIS RULE AND SUCH FARES WILL NOT NECESSARILY BE AVAILABLE ON ALL FLIGHTS. THE NUMBER OF SEATS, WHICH THE CARRIER SHALL MAKE AVAILABLE ON A GIVEN FLIGHT, WILL BE DETERMINED BY THE CARRIER'S BEST JUDGEMENT. OTHER CONDITIONS MILEAGE UPGRADE PERMITTED FOR BOOKING CLASSES B/Y/D/C/J. FOR FURTHER BOOKING CLASSES AND CONDITIONS CONTACT CARRIER FOR DETAILS.