Words matter. There are plenty of studies that show e.g. certain language in job listings discourages women from applying: https://qz.com/797559/gender-bias-job-listings-language/
When it can be reasonably proven that this is actually happening in this case. A reasonable start would be finding a real (as opposed to straw) person who feels "excluded".
If "bruh" is legitimately "excluding people from the community" in this context (And let's be honest here: a job posting is not equivalent in any way to a readme on a git repo), then by all means, let's have the conversation.
If it isn't? This is all just noise. Worse, actively harmful and distracting noise.
If "wat", "bruh" and "performance gainzzz" (of all things.. we're not talking about slurs here) in a readme actually gets people to self select out of using an update checker, I find it very hard to see that as anything other than a positive for people who want to work, rather than debate sociology.
...not that I think that was an intentional goal of the author.
Because I have a definition that states you use the best tool for the job at hand, rather than choosing (yes, choosing) to complain loudly about poorly-described-and-argued ancillary matters which don't directly impact the operation of said tool.
I reject the idea that "professionalism" means that the cheeky, mischevious humor that has basically defined the hacker spirit for decades must be stamped out or suppressed.