Voluntary self-modification also requires a pre-existing desire to self-modify.

People have motives to increase their status, so we can check this box. Of course, this depends on phenotype, and some people do this much more than others.

I wouldn't take a pill that made me want to initiate suicide attacks on people who insulted the prophet Mohammed, because I don't really care if people insult the prophet Mohammed enough to want to die in a suicide attack defending him.

You can't self-modify to an arbitrary belief, but you can self-modify towards other beliefs that are close to yours in belief space. See my comment about political writers. You can seek out political leaders, political groups, or even just friends, with beliefs slightly more radical than yours along a certain dimension (and you might be inspired to do so with just small exposure to them). Over time, your beliefs may shift.

If X doesn't offend you, why would self-modify to make X offend you to stop people from doing X, since X doesn't offend you?

To protect/raise the status of you yourself, or of a group you identify with. I proposed in that comment that people might enjoy feeling righteous while watching out for the interests of themselves and their in-group. When you get mad about stuff and complain about it, you feel like you are accomplishing something.

Thus, someone who responded with a cost/benefit calculation to all respectful and reasonable demands to stop offending, but continued getting touchy about disrespectful blame-based demands to stop offending, would be pretty hard to game.

The problem is that other people only care if you are with them or against them; they don't care about your calculation.

The second problem is that it can be hard to distinguish these two things. People who have a sufficiently valid beef might be justified in making blame-based demands to stop offending, and your demand that they sound "respectful" and "reasonable" is itself unreasonable. Of course, people without a valid beef will use this exact same reasoning about why you can't make a "tone argument" against them asking for them to sound more respectful and reasonable.

There might be a correlation between offense and the "validity" of the underlying issue, but this correlation is low enough that it can be hard to predict the validity of the underlying issue from how the offense reaction is expressed, which weakens the utility of the strategy you propose for identifying beefs.

However, your strategy might be useful as a Schelling Point for what sort of demands you'll accept from others.

One difference between this post and the original essay I wrote which more people liked was that the original made it clearer that this was more advice for how people who were offended should communicate their displeasure, and less advice for whether people accused of offense should stop.

It may have been tough to get the message, because the British salmon example is hypothetical. A real-world example of some group succeeding in claims of offensive might be useful.