The bug
The outline from the glowing effect does not render at all. The particles still render, though. This makes the glowing effect useless because you can't see the outline of mobs through blocks.
To reproduce
Please see this video:
[media]Linked issues
is duplicated by
Attachments
Comments

I can confirm.

Is this a Mac issue perhaps? I get glowing outlines with commands, as can be seen in the screenshot I attached.
Hmm, could be a Mac issue. I tested it on a Mac. I attached this screenshot as well as a crash report, so you could compare it to yours if you'd like.
[media](please excuse my messy bug testing world.)
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This issue seems to only occur whilst using a Mac. I've tested this multiple times on Windows 10 and have been unsuccessful in reproducing this bug.
I cannot reproduce using the Apple M1 chip with macOS 11.1. This is likely an issue with Intel graphics, rather than macOS.
I've attached a screenshot to prove that I cannot reproduce without Intel graphics.
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This is fixed in 21w10a! (MC-169921 still happens, though.)
Can confirm that this has been fixed 🙂
In 1.16.4, the glowing outline renders, but I experience MC-169921 and MC-177383. In 20w45a, the glowing outline does not render at all. Also, here is a crash report from a manually triggered debug crash:
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