Can someone on a proper computer hit F12 to bring up the developer console? I wonder if there's lots of angry red text, if both scripts and images are having issues.
I'm going to be honest, in spite of what my resume says, I'm not familiar with Javascript. There doesn't seem to be any big red signs indicating bugs in the developer console, but as we all know that doesn't mean there aren't bugs lurking in the code. Popping open the source code, I can see that there is something happening with the action bar on the posts that are unquotable.
Here is the second post ITT, which I can reply or quote:

It has all three actions in the action bar below the post. Compare to 0 1's first post:
Missing the two actions in the action bar below. It also has a broken select to quote:
And that's as far as my limited knowledge takes me. So for some reason, it appears that on these certain posts, they are losing the two actions in the action bar, and the select to quote feature is not working, despite apparently having the same classes as the posts that are quotable. I'm inclined to agree with Positron, it seems to have to do with post length as long posts and posts quoting long posts are affected. My own first post ITT is unquotable (why didn't anyone tell me?!) and so is the one directly above this one. I'm going to bet that this one will be as well.
For reference, I'm using Brave on Uwubuntu, and yes I use the kawaii theme.