Fundamentally I don't think it matters which mathematical operator we use for an operation that's not strictly mathematical (or at least most users don't think of as mathematical), everyone is quite happy with "x = 4" not having it's rigorous meaning of "x == 4". As long as there's a compact and clear way of doing string concatenation I'm happy.
If most people want * that's fine especially as there would need to be a very good reason to change it now. The point is that we should make it as easy as possible for people to transition to Julia from other languages, and this is one potential stumbling block. I agree with Tobias's suggestion of a REPL, IJulia only +(s1::String, s2::String) that throws an informative error. For my part I've updated Julia By Example <http://www.scolvin.com/juliabyexample/#Strings-Basics> to give an example and a link to this discussion.
