Why should the location of discussion affect its value?

Because the anonymity of the internet causes discussions to derail in aggressive posturing as many social restraints are absent. Also because much communication is non verbal. Also because the internet presents a low barrier for entry into the conversation.

Mostly, a communication has value separate from where it is posted (although the message is not independent from the messenger, e.g. with the advent of the internet scholarly articles often influence their field while being read by relevant people in the editing stages by peers and go unread in their final draft form) but all else equal, knowing where a conversation is taking place helps one guess at its value. So you are mostly right.

Recently, I heard a novel anti-singularity argument. That "...we have never witnessed a greater intelligence, therefore we have no evidence that one’s existence is possible.". Not that intelligence isn't very useful (a common but weak argument), but that one can't extrapolate beyond the smartest human ever and believe it likely that a slightly greater level of intelligence is possible. Talk about low barriers to entry into the conversation! This community is fortunately good at policing itself.

Now if only I could find an example of unnecessary status manoevering ;-).