Is there some phonetic value the first I adds to the word? Does "Eil" sound differently than "El"? It seems like it would have to, right, because aren't E and I are both slender vowels?
I'm not really hearing any. Is palatalization what that extra "i" typically adds?
It’s what any slender vowel typically adds. The difference between a broad consonant and its slender equivalent is usually (but not always) palatalization of the slender consonant.
But then back to the original question: what does the first "i" add to the word?
The possibility of spelling it in Irish; there are no Irish words that begin with el-.
Which is interesting. But does that mean the answer to my original question is "the first letter i adds no phonetic value to the word" then?