Diffusion highlight is really bright yellow, it is quite disturbing and really not homogene with other pastel-ish color on the website.
It has alaways striked me but I just react now based on @chad comment :

In T9583#140594, @chad wrote:

dat yellow

Won't it be better do change it for :

.diffusion-source tr.phabricator-source-highlight {
    background: #ffff00;
}

to :

.diffusion-source tr.phabricator-source-highlight {
    background: {$sh-yellowbackground};
}

on https://secure.phabricator.com/diffusion/P/browse/master/webroot/rsrc/css/application/diffusion/diffusion-source.css;4b43667086ae4faecb56bf54e0f743e53e0687a1$12-15

I tested on my work computer against different file and it seems to have even a better contrast.

If you do agree on a fix, please let me send you a diff.