When I uploaded a SVG file in response the SVG was small so I increased the scaling percentage (in the post) to 1000% to get it to a bigger size. The size did not increase linearly with the percentage entered. there seemed to be steps at which it jumped dramatically.
I don’t know why discourse does that or how it comes up with pixel size for SVG, but when you post them you can see whatever numbers it chooses and add some zeros and/or multiply by something big.
I think I have successfully audited the entire site for this problem, using the database and filesystem access to look for instances. Except for one DM thread, I think that I have resolved all instances of this by editing posts.
I didn’t notice that the 8x11 pixel rendering was not a dust mote on my screen and previously just changed it to a download link. I fixed it now to have a reasonable size.
This one was so small that I think it didn’t render at all, because it was 2 x 3 pixels of mostly white.