Here's the big reason GitHub should do it:
It makes the product better
I know people love to talk money and costs and "value", but HN is a space for developers, not the business people. Our primary concern, as developers, is to make the product better. The business people need us to make the product better, keep the company growing, and beat out the competition. We need them to keep us from fixating on things that are useful but low priority and ensuring we keep having money. The contention between us is good, it keeps balance. It even ensures things keep getting better even if an effective monopoly forms as they still need us, the developers, to make the company continue growing (look at monopolies people aren't angry at and how they're different). And they need us more than we need them.So I'd argue it's the responsibility of the developers, hired by GitHub, to create this feature because it makes the product better. Because that's the thing you've been hired for: to make the product better. Your concern isn't about the money, your concern is about the product. That's what you're hired for.
I'd say that this is also true from a money-and-costs-and-value perspective. Sure, all press is good press... but any number of stakeholders would agree that "we got some mindshare by proactively protecting against an emerging threat" is higher-ROI press than "Ars did a piece on how widespread this problem is, and we're mentioned in the context of our interface making the attack hard to detect."
And when the incremental cost to build a feature is low in an age of agentic AI, there should be no barrier to a member of the technical staff (and hopefully they're not divided into devs/test/PM like in decades past) putting a prototype together for this.
At the end of the day it boils down to putting your users first.
Making the product better generally stems from acting in their interest, honing the tool you offer to provide the best possible experience, and making business decisions that respect their dignity.
Your comment talks a lot about product and I agree with it, I just mentioned this so we don't lose sight of the fact this is ultimately about people.
> Your concern isn't about the money, your concern is about the product. That's what you're hired for.
According to whom? Certainly not the people did the hiring.
I somewhat agree that developers should optimize for something other than pure monetary value, but it has nothing to do with the hiring relationship, just the moral duty to use what power you have to make the world better. In general, this can easily conflict with "what you're hired for."
In this case I think showing suspicious (or even all) invisible Unicode in PRs is even a monetarily valuable feature, so the moral angle is mostly moot. And I would put the primary moral burden primarily on the product management either way, since they're the ones with the most power to affect the product, potentially either ordering the right thing to be done or stopping the devs when they try to do it on their own.