[SOLVED] Why is this xorg.conf line highlighted?

If I uncomment this line it does apparently work, tapping is enabled, so why is it highlighted when I read xorg.conf in nano?

I'm not sure this section of my xorg.conf is quite correct (I haven't pursued commands for all the extra touchpad functions because I've never used them) but the form I've used seems correct. There is a slight lag compared to the same function on a laptop that has a Synaptics touchpad and compared to using hotkeys, so maybe these are related?

Thanks.
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