For me, when someone is critical of another person having spent their time checking out if there are any optimisations for something submitted to HN with, lets face it, snarky, "Well, raise a PR then", that's quite a shame.
I read that comment as, "rip huge chunks of Bootstrap and jQuery out of it - should be quick"... well I am guessing given Bootstrap design patterns that they used these tools as a core library in-which they built their site around. They may be planning to leverage these tools in the future, or even just want to give themselves the option to... It's an over-simplification. Likely, this site got them to where they wanted to be... a much more modern-looking site without a ton of effort sunk into development.
It's also completely disingenuous to talk about these filesizes in pre-gzip numbers vs. post. When you look at these "optimizations" without taking into account gzip you are looking at a "worst case scenario" that doesn't exist - this site is gzipping it's assets over the wire. The jQuery gripe is more like 33.6Kb vs 96Kb when you look at it through the gzip lens.
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This sort of response (and subsequent defense) is why I would never show my creations here. It's emotionally difficult for me to see such a stable and mature project as Munin accomplish a bit of modernization only to be nitpicked like this. Munin is a great tool.
"Raise a PR" is perfectly valid here when it comes down to it. I think the internet will handle the extra ~100Kb/page load just fine.
If that's the case then creating a PR and raising it would be a waste of time, as it'd be rejected.
Whether it's a website or some other open source project, maintainers usually don't like it when you create a massive refactoring PR without talking with them first.
If, luckily, the maintainers are on HN, I guess talking about the "problem" here could very well substitute for raising an issue on whatever platform they use.
Basically the same a pointing out a spelling error on a single slide in a CS class. You are technically correct about the feedback, but it is misplaced and not worth spending time on in class.