A couple of issues I've been having.
The first is a long standing one. When posting from my Windows 10 laptop using Chrome (V. 75.0.3770.100) I have all sorts of problems when copy/pasting quote blocks. It is a consistent problem. The first attempt to paste (either by right-clicking and selecting paste or by Ctrl+V) appears to have no effect. The second paste does work. However, I find that hidden in the ether of the bottom of the text box is a second copy of the quote, but it is completely inaccessible and invisible until I hit post, after which it appears at the bottom of my post. This isn't usually a problem as the multi-quote function provides the functionality I need for the most part, but there are occasions when I do need to copy/paste quote blocks such as when issuing warnings. The only way round it I have found is to do the following. Before posting, I must place my cursor at the end of my post, and then hold Delete, which will then drag the extra quote out of the ether and slowly remove all of it.
The second is that even the standard youtube links are not automatically embedding.
Here's an example posted as plain text straight from my browser address bar:
I know that mobile links won't work, but I've always been told that the standard link should work.