Erm, it's not empty and they 'grey out' the button if you remove all the text.
I guess it's an attempt to get people to leave a constructive comment but as ever 'pink and fuffyness' prevails and you're not forced to do so.
To be honest I frequently find it difficult not to
s/about/a steaming pile of shit./
but whilst it would go down well with the regulars just imagine the whingeing it would cause here on meta so I go with,
s/ about/./