Titiatio is (to my mind) not an elegant solution. Why not the imperative titia, as in audi, the car manufacturer? Still, “twitter” has two syllables, so the verb trissare would be better, in the imperative as trissa, or as trisso (“I twitter”). But my real question is this: Why so conservative? These verbs are all onomatopoetic. So why not create your own verb? Because it’s not in the “official” dictionaries? Come on! I propose the imperative tuitta, based on tuittare, tuitto, tuittas, tuittavi, tuittatum, with a contracted nominal participle tuittum, with derivatives like tuittator etc. 🙂 It’s not even a complete neologism, because there’s a similar word in Greek τιττύω, as known from the double-onomatopoetic compound τιττῠβίζω (“to twitter”). Apply a simple metathesis to tittúô, latinize, and you have tuitto as an alternative to titio. Voilà. 🙂