While I'm not personally offended by anyone saying any of these things, I will say that it feels like a lot of these are said by rote and not actually meant - this isn't necessarily a bad thing, we do it all the time. The cashier who tells you to have a nice day is saying it by rote. You may not care much about what a workmate you barely know did on the weekend, but you might ask them about it while you're riding an elevator up with them to your office. They're social conventions, and I don't really have a problem with doing them, though in all honesty, in my mind I find them a bit of a waste of time. I was told once that this may be part of my makeup as an introvert, which means I may find social interactions tiring, and honestly, I do find it a struggle making small talk (and so there are times when I don't ask my workmate about their weekend, but I will still respond politely if they ask me).
That said, I personally reserve the sentiment of "gg" for games I actually thought were good, hard fought, well-played, etc. Typically these are close games, but there's nothing to say that (as another player mentioned), someone who makes an effort to come back to at least a reasonable score after tanking badly in the first few turns couldn't be acknowledged as playing a good game as well. Whatever that means for you. If you want to say it on every game, sure. I do also tend to respond back where people say it to me, as I feel an expectation (from myself) to do so. Although if it's been more than 2 hours since the game concluded and they posted their message, I don't worry about it, because when I get those random messages hours after a game ends, I just find them confusing and annoying. I also don't respond to "gl hf" with the same, as I feel like doing that would be disingenuous, because I'm only saying it because they do (I don't usually initiate it).
I will admit (and have said this before) that when I find myself matched against the same player (eg. in Arena) for 3+ games in a row, and each time they open with "gl hf" and close with "gg", with no changes to interactions, I start to find them disingenuous, and at that point I'm pretty sure they're said by rote, and not really meant. Others have pointed out that maybe my opponent hasn't noticed that they're playing the same person again, and if they have multiple tables (especially of the same game), that's probably fair enough. The thing is, everyone has their own style of play, and while I'm sure that there are things that are said as pleasantries and not well-considered (and perhaps shouldn't be said in some cases as they can come off as passive aggressive), is it really that big of a deal? And I have a similar reaction to those who post threads bemoaning the lack of conversation (or even pleasantries) as some indication that society has gone to the dogs. Do what makes you happy, and unless people are outright insulting to you, you should probably give them the benefit of the doubt as generally good people who just want to play games (much like you, one assumes).
