Well, i think that all elven swords glow when there are orcs nearby.It was ability that was said like: It glowed when there were orcs nearby, because it was elven sword or something like that.That doesn't make sense if it was rare ability amongst elven swords.
I' would like something more than : No, you're wrong answers.And that dialogue was not Tolkien's own that's sure
... puts me off when i see people being harsh