Works for surrogate pairs

IsPalindrome.cs

static bool IsPalin(string s)
{
    var bi = s.Length - 1;
    foreach (var r in s.EnumerateRunes())
    {
        if (!Rune.TryGetRuneAt(s, bi - (r.Utf16SequenceLength - 1), out var b) || !r.Equals(b))
        {
            return false;
        }

        bi -= r.Utf16SequenceLength;
    }
    return true;
}