Whatever argument you have in mind about "the measure of those worlds" will go through just the same if you replace it with "the probability of the world being that way". You should be exactly equally concerned with or without MWI.
The question that actually matters to you should be something like: Are people with such intrusive thoughts who aren't generally suicidal more likely to jump in front of trains? I think I remember reading that the answer is no; if it turns out to be yes (or if you find those thoughts disturbing) then you might want to look into CBT or something; but MWI doesn't have anything to do with it except that maybe something about it bothers you psychologically.
Okay, fair enough, forget the whole increasing of measure thing for now. There's still the fact that every time I go to the subway, there's a world where I jump in front of it. That for sure happens. I'm obviously not suggesting anything dumb like avoiding subways, that's not my point at all. It's just...that doesn't seem very "normal" to me, somehow. MWI gives this weird new weight to all counterfactuals that seems like it makes an actual difference (not in terms of any actual predictions, but psychologically - and psychology is all we're talkin...
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
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