Hmm...

Are you sure that you fully understood my last post? I know that the punchline looks like I'm suggesting option 3, but, I'm not. In fact, if you go over all of my thinking on this, you'll see that at both points in time (back in December, and now in March) I've basically been inclined to leave TalkImg's default BBCode without any dimension information at all. Back in December that's where I landed because I felt like we didn't know whether or not including just the height attribute would actually help to reduce layout shifts, which is why I said: "So, you should probably do nothing until someone tests that hypothesis.", and now in March that's where I land again (but this time, it's because of the issue that Loyce pointed out; that is, I suspect that it's actually the height attribute that sometimes interacts poorly with the forum's responsive down-sizing of images).

I know that I have a tendency to explain my thinking in kind of a tiresome way, so please don't feel bad if you did misunderstand me. (That is, I expect people to linearly digest each sentence, like I do when I'm reading someone else's thoughts on something, but, I realize that that's incompatible with the modern tendency to just quickly skim over things while pausing at the relevant-looking bits in the hopes of being able to pick up the gist of what someone is saying.)