It's like a link but with an ! added to the front. Actually I think you can do alt text (ie image description for eg. screen readers) like this 
The image is hosted on a different site. Personally I feel like a dedicated image hosting site is more likely to be around in a year than the average Lemmy instance, so I'll probably use links over direct uploads most if the time. I already have at least one post of a direct upload that no longer has the image
Yeah that's my comment 😀 And as I and the other person pointed out, the image isn't on a Lemmy instance, it's coming straight from imgflip and just getting embedded in the comment
Reddit is forcing mods to open subs back up. So to continue protesting, individual redditors are just shit posting to make their subs effectively useless. Some subs are getting really creative with it too. r/steam is posting about literal steam and r/interestingasfuck has opened posts up to pornographic content. It's rather amusing.
It's more about making the sub useless than it is about making sense. So only posting pics of sexy John Oliver devalues the purpose of a subreddit... Unless that's what people want from now on.