Elevated brain glutamate levels are associated with migraines, but there’s no solid evidence that dietary glutamate is a trigger for migraines.

The number of people avoiding it is not evidence of anything other than public perception.

Elimination diets are also super impressive.

I agree on all your points. If someone suffers from migraines, though, it’s worth trying figuring out plausible triggers even if the evidence isn’t really solid.

It’s important not to conflate ingredients when doing an elimination diet, though. Separating restaurants or prepackaged foods at home that use MSG from those that use a lot of salt (or preservatives, or artificial dyes, or “natural flavors”, or any number of other things) is pretty difficult. I’ve seen several instances over the years of people assuming a restaurant used MSG based on getting a migraine, even when that restaurant doesn’t use MSG in any of their dishes. I’m not even a doctor, just an interested person with migraines. I’m sure a nutritionist or headache specialist could tell us stories.