In terms of HN’s overt purpose, it is.
> it's a valid market signal
Every expression of anyone's reaction to a brand is “valid market signal” on the level that that is true of this, but that doesn't stop most of that from being noise in an HN comment thread.
> So I'll side with automatically appending one such comment in every Google thread until their behavior visibly changes.
Such an automated comment would still be noise, but would have less of excuse of being a valid market signal than comments posted organically, even if that was an excuse (which it's not.)
In the past, many companies have had "not great" reputations for supporting products, but surely Google have taken it to level not seen before. The fact that pretty much all of their products live in the cloud rather than being software that can continue to be used beyond the support period (ala Win98) has probably contributed a lot to that. I think the way that potential customers react to that reputation is very interesting.
We're at the point now where Google have clearly acquired this reputation and it's very likely to affect the adoption of anything they try to launch. The next phase will be Google recognising that and trying to correct it somehow. I'm keen to follow along and see how that goes.