Like I said, if they're really doing this, that's great. But are they really committed enough to this to let a great candidate go when the non-negotiable number is too low? Is this just for peon-level employees, or executives too? That's the real test.
That said, I suspect "outside signaling" will become a huge thing. You tell your recruiter you need $X, your recruiter tells Reddit that you need $X, you get offered $X, how convenient for both you and Reddit! On the executive side, over dinner you discuss what it would take you to leave your current company -- of course, not negotiating, just two people talking -- and low and behold, the offer will be exactly what was discussed, of course, no negotiating.
They've been subtly undermining the original promise of the site in various ways. /r/Undelete is a good example of one symptom of the problem. They need to figure out a different way of structuring Reddit's moderation and stop trying to sugar coat things that are clearly financial decisions. The timing of the announcement seems more angled to cash in on sympathy for Ellen Pao than it is an honest desire to "solve" the salary negotiation gap. She has been working with Reddit since 2013, after all.
If it was born from honest desire, they'd have done it sooner and they'd do it like Buffer does [with a transparent salary position list]. The way they've done it they can still pretend there is no negotiation even when they've created a clear loophole for them to make "exceptions".
This isn't so much to attack the way this was handled but more to point out Reddit now engages in the kind of corporate doublespeak that people who are passionate seek to avoid.
Such a measure will also mean that aggressive salary negotiators will go elsewhere after their attempts at negotiation are rejected by Reddit HR. Since these people are almost always male, that's a win. It will result in a workplace with less men : )
Eliminating salary negoiation just because woman are not good at is stupid. It baby's them.
The whole premise that people - women or men - are not to participate in determining their future with the company, at least in the compensation aspect, but only can be externally evaluated, given something and have no further input in the process but either blindly accept whatever they are given or hit the road - sounds kind of demeaning to me. Negotiation is part of what mature adults do to arrive to commonly acceptable goal. Saying "here's your allowance and not a dime more" is how a parent communicates to a child. Not an equal standing.
Instead of talking the first low ball offer, they'll get what reddit thinks they are really worth. Which is still probably lower than what they could have negotiated.