I wasn't aware of it at all until I got home a little bit ago, and haven't seen any mention of it in the forums (or GOG's front page...), so I figure most other people missed it, too, unless they frequent Twitch.tv/GOGcom.

The stream is still going for the moment (Kilgore_Tr0ut is still streaming Planescape: Torment, but the interview is done and Avellone's gone. The VOD of the stream-up-till-now is here.

This should have been advertised by GOG. x-P

Yeah, just checked Twitter, and there was a tweet about 6 hours ago; maybe it was mentioned on Facebook, too. But I think there are a lot of other forum regulars besides me who don't do social media, and might not watch Twitch streams very often, and who were, therefore, probably were entirely unaware of it, as I was. (In my opinion, GOG should have made a brief news post about it on the front page, in lieu of the rather lame "article" they put up today.)
EDIT: Added words.

On another note, I should also probably declare that I have not seen any of the interview, and haven't watched much of Kilgore_Tr0ut before, so I make no guarantees about the quality of the interview. =)

Well at least the social media posts were something; I agree that a newspost should have happened though, but perhaps it was mentioned in the stickied Twitch thread.

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Nooope, I was the last person to post there, and that was a few days ago.

It most likely was, just not on the mostly abandoned forums where we old grumps are left to rot.
Stuff like that makes this place here feel like a hospice for the old customer base.

PS: I don't do any (anti-)social network stuff either.