We don't even have a consensus on things like Newcomb's problem, free will or dust specks, let alone stylistic preferences. Were I to hypothesize about all the possible reasons why one of 1000+ people might down vote me that are not obvious in the way a Schelling point would be and calculate the probabilities of each, I would be spending an incredible amount of time just to figure out that you didn't like a particular turn of phrase.

This is true, the overhead for adopting and learning somewhat arbitrary cultural norms can be significant. This is particularly the case for those whose instincts are less finely targeted towards social conformance. This is a class predictably overrepresented on less wrong. That said, you have now had the preference explained to you in clear English. The need for calculating probabilities for countless hypothetical downvote causes is largely removed and this one hypothesis "Saying +1 Karma causes some downvotes" is now comfortably high. Now it is a choice whether you want to spend emotional effort fighting that norm or whether you let it go and adapt.

There are many times where it worthwhile to fight the tide and attempt to influence social norms in a desired direction. I do this constantly in my battle against what I call bullshit. However it is important to chose one's battles. In no small part because if one spends their influence attempting to fight irrelevant things then there is less credibility remaining for fighting the battles that matter.

In this case people don't like "+1 karma" as part of a general distaste for all unnecessary references to the karma based meta-level. I expect that if you had responded "Ok, thank you for explaining. I'll adopt different word use in my reinforcement." then you would have been upvoted and also had people reverse their downvotes of the earlier comment. People being cooperative and updating tends to be appreciated.

I personally request that you change this detail of style rather than escalating your dissent. It is frustrating to watch otherwise rational people undermining their credibility due to what amounts to social awkwardness. Lose gracefully on small things so that you win more things that matter.