“I never notice when Go players brag.” I’m not really sure if that warrants advice, but since I’m so inclined, I’ll deliver. Read the chat more frequently.
If there’s a bias toward ironing out mistakes instead of celebrating successes in Go, I would conjecture that it’s very simple to predict future failures in games and very hard to predict really any form of future successes, therefore it would more frequently come as a surprise when people register a success. If you’re surprised, you’re unlikely to have been confident about it and if you weren’t confident, it may seem illogical to take credit for the ostensibly remarkable result, unsurprisingly resembling the definition of humility.
If your point is that even adjusting for how easy it is to (have someone help to) detect failures, we (i.e. you) should see more success reports, I would hypothesize that it is rather uninteresting for anyone to be lauded for their personal achievement (as you implicitly realize by using the negatively loaded term).
We are left with the question of what purpose “bragging” serves. Again I would hypothesize that it serves to inspect the relationship between “praise requester” and “praise giver”, mostly because it would be uninteresting if the former was solely motivated by the need to disseminate a factual statement (which therefore does not require affirmation), despite the fact that I deem it a legitimate reason (“I made it to 1d.” - Yes, you did).
It follows that if you don’t see ‘motivated statements of success’, it’s either because you literally do not witness them or because no one tells you about them. The former would be likely if we assume low prior probabilities for the relevant factors P(people are successful) * P(people have a motivation to tell) * P(you are able to witness) - where ‘able to witness’ includes detecting and identifying unobvious/indirect/encrypted ‘bragging events’.
The extension of this model would return to focus on the question of motivation - and serve an explanation for the latter option. If it was indeed to inspect the relationship with the prospective ‘praise giver’ (i.e. indirectly asking “do you care about me?”) it might simply be that (if you literally don’t get to see any praise requests) no one cares about your praise.