I found a clipboard analyser program for the Mac, and can see the raw contents of the clipboard that is being pasted. There’s no HTML format, but there is an RTF format, and I’m guessing that’s what’s being used. Here’s what the RTF clipboard contents look like:
{\rtf1\ansi\ansicpg1252\cocoartf2577
\cocoatextscaling0\cocoaplatform0{\fonttbl\f0\fnil\fcharset0 .AppleSystemUIFontRounded-Regular;}
{\colortbl;\red255\green255\blue255;\red0\green0\blue0;}
{\*\expandedcolortbl;;\cssrgb\c0\c0\c0\c84706\cname labelColor;}
\pard\tx560\tx1120\tx1680\tx2240\tx2800\tx3360\tx3920\tx4480\tx5040\tx5600\tx6160\tx6720\pardirnatural\partightenfactor0
\f0\fs26 \cf2 Test}
Aside from RTF, there just the plain text in both UTF-8 and UTF-16 format. So I’m pretty sure Obsidian is somehow trying to import the RTF formatted clipboard data, and it’s getting confused somehow.
Anyway, there are no extra spaces or paragraphs that I can see in the RTF…and pasting this into other applications work as expected. It’s just Obsidian that seems to have trouble with this RTF-format clipboard.