qqplot

That's not what qqline() does and for good reason - it treats
x and y asymmetrically.

But qqline() is a very simple function, using the quartiles
as also suggested by John. Here's a modified version that
should work for Carol:

qqline2 <- function (x, y, ...)
{
    y <- quantile(y[!is.na(y)], c(0.25, 0.75))
    x <- quantile(x[!is.na(x)], c(0.25, 0.75))
    slope <- diff(y)/diff(x)
    int <- y[1L] - slope * x[1L]
    abline(int, slope, ...)
}

I've just replaced the line using Normal quantiles with
the quantiles of x (and omitted the datax option).