Focusing on issue (2) for the moment, RE display:none on same-doc SVG filters: (1) it looks like bug 376027 tracks a similar (maybe the same?) longstanding issue. (2) It looks like there was a 2019 SVG Working Group resolution quoted in https://bugzilla.mozilla.org/show_bug.cgi?id=1463336#c1 which says essentially that the element should be treated as if it did not have a filter, which happens to match what we do for CanvasRenderingContext2D.filter (but doesn't match what we're doing for CSS `filter`). So: in that part of the reporter's original testcase, Firefox is compliant and Chrome is noncompliant in honoring the filter, I think. (We are still wrong to hide the element when the filter is applied via CSS, which is what bug 1463336 is about.)
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Focusing on issue (2) for the moment, RE display:none on same-doc SVG filters, I dug a bit and found two associated bugs: (a) it looks like bug 376027 tracks a similar (maybe the same?) longstanding issue. (b) It looks like there was a 2019 SVG Working Group resolution quoted in https://bugzilla.mozilla.org/show_bug.cgi?id=1463336#c1 which says essentially that the element should be treated as if it did not have a filter, which happens to match what we do for CanvasRenderingContext2D.filter (but doesn't match what we're doing for CSS `filter`). So: in that part of the reporter's original testcase, Firefox is compliant and Chrome is noncompliant in honoring the filter, I think. (We are still wrong to hide the element when the filter is applied via CSS, which is what bug 1463336 is about.)