`preview-hidden-comments` includes the whole comment in the preview #4524

I tried "troubleshooting" this. My finding:

• First of all, what's "unusual" with this comment by me (and hidden by me), is its <details> which contains a <code> block
• There are no console errors.
• (in a fresh Chrome profile with only RG having login to GitHub) I copied-pasted these two comments in a test PR (as draft/non-draft) in my own test repo, where (as admin, I can unhide them) and they are rendered ok: Therefore, if it helps, the only difference I can spot between the linked PR in the RG repo and a PR in my test repo, is that in the RG repo, once I hide a comment, I can't unhide it.

Disabled via hotfix, I'm seeing a even-worse behavior in on https://github.com/darkred/test/pull/6

Thank you for looking into it @darkred, but this is what I see, I don’t think it depends on whether one can hide the comments:

<img width="1161" alt="Screen Shot 4" src="https://user-images.githubusercontent.com/1402241/124352032-18ee3900-dc28-11eb-9fa2-d88e5fd85e10.png">

And this is Chrome too, Refined GitHub just installed in a semi-new profile:

<img width="975" alt="Screen Shot" src="https://user-images.githubusercontent.com/1402241/124352124-b184b900-dc28-11eb-8329-ae04c9c0a08a.png">

As a fix, 2 changes are necessary:

• limit the text via JS, like ${commentText.slice(100)}}</span>`
• fix the CSS that was used to enable the ellipsis
• ensure that the "Show comment" toggle stays on the right side instead of collapsing

Test comment

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