"start writing a comment and give up halfway through" gang rise up

Honestly, it is also fine to simply... not post. I spent my first year on the site pretty much purely lurking, and even after I started actively posting it mostly consisted of random fluff I found fun or interesting. And I still make way more video/image posts than comments or text posts, precisely because it doesn't involve any writing of text - as soon as I get into that territory, it takes me like half an hour to post something since I have to rewrite every sentence a dozen times.

So, you can try that route, echoing Alaskaball's advice - if it's something you thought was neat, just post it. If even just one other person sees it and thinks "huh, that's neat", then maybe it was worth mentioning.