i have, quite a bit, over the years. besides making my own (Glaugnea), i have written in Klingon, Taneraic (which i especially recommend for its vocabulary), an early form of Vorlin, Volapuk, & of course Lojban (which i have written 3 short books in). for years i wrote in nothing but Esperanto during the "dog days". there was a project in which the portmanteau words created by artists ("pwoermds") received my inscrutable definitions--the internalational contradictionary--some form of it may still be online somewhere.
i like to make up new meanings, & name things that have not yet been distinguished by existing language. in retrospect, it seems that i have been trying to make up for the shortcomings of natural language to describe my own experience.
not much time right now, & for awhile. the internet has made me very aware of all the people out there with similar interests; some of them are amazing.
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"I have always found that Angels have the vanity
to speak of themselves as the only wise; this they
do with a confident insolence sprouting from systematic
reasoning." --William Blake