I found the not-real-culprit: `gfx.downloadable_fonts.otl_validation=false`, which is true on nightly and false on stable Firefox. And with the validation on, Firefox just rejects the "tabler-icons" font that Misskey uses. This has been known for a while. [1](https://github.com/tabler/tabler-icons/issues/476) [2](https://github.com/webcompat/web-bugs/issues/118081) And with the validation pref off, it seems the real culprit is that the tabler-icons Misskey uses is somehow expensive to render on Firefox? Keeping the NI to jfkthame for that bit.
Bug 1912660 Comment 6 Edit History
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I found the not-real-culprit: `gfx.downloadable_fonts.otl_validation=false`, which is true on nightly and false on stable Firefox. And with the validation on, Firefox just rejects the "tabler-icons" font that Misskey uses. This has been known for a while. [1](https://github.com/tabler/tabler-icons/issues/476) [2](https://github.com/webcompat/web-bugs/issues/118081) And with the validation pref off, it seems the real culprit is that the tabler-icons font is somehow expensive to render on Firefox? Keeping the NI to jfkthame for that bit.