NOTE: I reported this bug on a different forum at first, but somebody told me it should probably go on here. This post is directly copied from that forum.
This is a rather obscure issue, but if you try and do something like this in HTML
<blockquote>
<p><img style="display=inline-block;" src="upload://tbEylS4iHyycxJFPT1cnaUFc17U.png" alt="Check" data-base62-sha1="tbEylS4iHyycxJFPT1cnaUFc17U" width="15" height="15"> Solved by <a href="https://meta.discourse.org/u/pixlz/summary">Pixlz</a> in <a href="https://discourse.theme-creator.io/c/junk/16?preview_theme_id=6379">post #1</a></p>
</blockquote>
Just for the funny in a PM to trick some friends, it should work like this. (taken from a discourse test site)
It works for 5 minutes, but @system auto edits it and it breaks, turning into markdown.
Note that Discourse also does this, but it weirdly doesn’t break like it does here.
Trying to put the upload:// as the image doesn’t work, it only works on a real website, which is why it isn’t working.
It ends up doing this for some reason, it changes after about 5 minutes
What I posted is just an example of this, it does it to any image embedded within HTML.
original thread on that forum, as I said I was told that this should probably go here instead, because it’s a default behavior of system.