I think the main problem here is that it's just difficult to use best practices because the software running this website does not use best practices.
What we do here is called
hotlinking (or inline-linking) and it's considered a bad practice in general. Some websites have resorted to some hostile behavior to prevent it, as it costs these third-party websites real money in bandwidth terms. Thankfully, since demand for hotlinking is so high, there are
multiple site who have hotlinking as their business model. The most predominate website to do this, by far, is
Imgur. Self-hosted sites like google photos, flickr, and others are probably fine, but you'll want to actually check their terms of service to make sure you're allowed to hotlink to your own photos.
The sizing of photos is another deeply frustrating aspect of the software used here. I've spent some time developing a browser extension that fixes this (among other issues) that I link to in my signature. Some of the benefits to the extension is that images are 100% width sized if they are too big to fit, and quoted images are shrunk to a very small size so they keep quotations compact.
The browsers supported are just Firefox and Chrome, I would implore anyone not using one of those browsers to switch, unless you're using, say, Brave or some other technical use browser.