It seems that both short and long [i] survived from Primitive Elvish in both dialects of Danian (PE19/25). In addition, [j] became [i] in Ossiriandic both initially and medially (PE19/19, 23), though it is possible that the change initially was simply an orthographic convention similar to Noldorin [j], written “i” initially.
References ✧ PE19/19, 23
|ᴹ✶-khj- > -(i)||[-kʰj-] > [-xj-] > [-j-] > [-i-]||✧ PE19/23|
||✧ PE19/19 (j- > i-); PE19/23 (-j- > -i-)|