SYSTEM INFO:
Obsidian version: v1.4.13
Installer version: v1.4.13
Operating system: Darwin Kernel Version 22.3.0: Thu Jan 5 20:49:43 PST 2023; root:xnu-8792.81.2~2/RELEASE_ARM64_T8103 22.3.0
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Community theme: none
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I can reproduce this if the image is very large, and is larger than the text readable line length.
If the image size is reduced smaller than the readable line length, then the gap disappears.
If I turn “Readable line length” off, and I resize the image to be larger than the pane’s width, then the gap appears again.
I can’t recreate this in the Sandbox vault. But I did turn off community plugins, and am using the default theme. So it might be related to some setting.
Here is a gif of resizing the screen, until the image is larger than the pane. The gap appears.
I can confirm you observations about resizing the image.
I can also recreate the same behavior in the Sandbox.
I would add that with the default “fit to pane” behavior the gap also appears if the original image is larger than the pane, even though it visually fits the pane.