It would be nice to combine this a bit with the selector passed into diffReviewableView. How about this in the variable definitions:

var elementName = 'file' + diffReviewable.get('fileDiffID'),
    diffReviewableView = new RB.DiffReviewableView({
        el: $('#' + elementName'),
        model: diffReviewable
    }),
    ...

This could also be defined in the initial variable definition instead of as a separate statement.

Spacing is a bit weird here. Add a space between if and (, and remove one of the two after &&.

Please add spaces around the + characters.

Put the })); on the next line.

You should probably merge the code above with this--we don't want to add a second anchor if one already exists, and it would be nice to keep these things next to each other.

You use this hex color in two places--mind defining a variable for it in defs.less?
Also, add a space after the :

This should use a variable for the color, and include a space after the :

This should use a variable for the color, and include a space after the :

This should use a variable for the color, and include a space after the :

This is closer, but still doesn't do quite the right thing for the case of comment anchors which are added by the template. I think probably what you need is something more like the following. Note that I haven't tested it, it's just a proposal for how to structure this code.

if (this._startAtAnchorName) {
    $anchor = $('a[name]"' + this._startAtAnchorName + '"]');

    /*
     * Some anchors are added by the template (such as those at
     * comment locations), but not all are. If the anchor isn't found,
     * but the URL hash is indicating that we want to start at a
     * location within this file, add the anchor.
     * /
    if ($anchor.length === 0 &&
        urlSplit.length === 2 &&
        elementName === urlSplit[0]) {
        $anchor = $(this.anchorTemplate({
            anchorName: this._startAtAnchorName
        });

        diffReviewableView.$el
            .find("tr[line='" + urlSplit[1] + "'])
                .addClass('highlight-anchor')
                .append($anchor);
    }

    if ($anchor.length !== 0) {
        this.selectAnchor($anchor);
        this._startAtAnchorName = null;
    }
}

There are a ton of typos in this comment.

Just a couple small changes left!

This change exposed an existing bug in the code. If the URL contains any hash, we want to strip it out here (otherwise if you copy a URL from a page which was navigated to you might end up with something like "diff/1/file1672,3#file1672,4" which doesn't work. Can you change this to just be if (window.location.hash) ?

If this._startAtAnchorName is null, this line will fail (and break the diff viewer). Can you change this line to just define the variable, and then assign it within the if (this._startAtAnchorName) block?

Ship It!