You can click the X on that other person's "Code-Review [+1 Their Name (X)]" label in the metadata section.

the X only shows up for my own votes, not for others

All logged-in public users should be granted the ability to set other people's CQ vote to zero: https://chromium.googlesource.com/chromium/src/+/refs/meta/config/project.config#22

I also verified that vmpstr@ (another chrome committer with no other special powers) was able to remove my CQ vote from one of his changes.

However, my @gmail account doesn't seem to have the ability to remove other people's CQ votes, so something is wrong. Investigating further.

Can you provide a link to a CL where you ran into this?

e.g. https://chromium-review.googlesource.com/c/chromium/src/+/800619 (screenshot attached)

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	gerrit.png 385 KB View Download

Oh, I see what's going on here. For some reason I thought that gerrit:6455 had been fixed, and this was something else. Unfortunately, this is a big underlying issue in Gerrit. I'm talking to them now about the fastest way to get gerrit:6455 fixed.