trustable, not a word. or, an invented word, but it does get the point across. "to be trusted" would be a better choice of words. point for you! thanks!

diction, though, relates to word choice and enunciation, not to the use of made up words. if we are claiming that this word is not really a word, which, in fact is true (as conceded above) then diction wouldn't apply as diction only relates to the use of actual words. aha, point for me.

we both win.