Different colour meanings

I don't think it's a question of the thread-depth line indicator.

If I'm understanding @TheShitAbyss's question, I see the same thing in some threads, where some comments have a plain white background, and others have a pale yellow background. (The colouring may be theme dependent. I haven't investigated that, but suffice to say that there are sometimes two different background colours on posts' comments.)

This post has examples: [Lemmy.ca Discussion] What should we do about Lemmit.online.

At first I thought it had to do with commenters coming from local instance (lemmy.ca) or other, remote instance, but that doesn't seem to bear out.

Then I thought it might be an indicator of top-level comment vs. reply comment, but in that post linked above, while most top-level comments are white, at least one has the yellow background (I sorted by Hot). There are replies to top-level comments also in both colours, in some cases even same-level replies to a comment, where two adjacent same-level replies have different backgrounds.

Here's a snippet/screenshot:

(Edit: well, darn. That screenshot doesn't serve much purpose because it's being resized down and I don't know how to circumvent that. It's just a 778x941 48KB static gif uploaded to an image hosting site with a Do Not Resize My Upload option. So I'm assuming the resizing is happening on lemmy.ca server-side. Oh well. I refer interested readers to the post linked above, where this screenshot comes from.)

I'm not great at pattern detection. If there is a pattern and someone wants to crack it, or already knows what the colours mean because it's blatantly obvious (or even explained somewhere(!)), I'm all ears.