Friday, 12 February 2016, 10:19am +00:00 from Greg Chalik <mrg3105@gmail.com>:

Lets focus :-)
1. Why are we sure the future common language is English-based? Because Marc wrote so?

Ummm, and Terry McInnes in the article I quoted. ;-)

But more than that, and more even than in other descriptions of Galanglic being based on English that are kicking around (and the Anglic bit of the name being a clue).  It's in the very names of worlds and characters throughout the Third Imperium (and other milieux) and often many other alternate universes that exist in publication.  It may be imperialistic, in the old sense of the word, and it may be parochial or lacking in imagination, and it may even be undesirable, but I would say it's clearly in the very DNA of Traveller and the Third Imperium.

tc