You might have noticed that there are a couple of different looking editor windows here on WordPress.
The main one is of course the Post Editor, which is actually pretty nice at putting together a good looking Blog Post, which is what we are doing when we start a thread.
Comments, on the other hand, are more restricted. However, it turns out that there are two kinds of comment editor windows. If you are viewing the threaded forum, the classic Habitable zone look, and click on reply, you’ll get the stripped down version. IT is possible to use html here, but I’ve not quite mastered it.
Instead, go to the Dashboard view by wither clicking on Dashboard, or comments, or pages. Find the post you want to comment on and use the reply button at the bottom of the post. Now you’ll have an editor that has very handy buttons for common html tags.
To insert an imag, click on the “img” button. You may have to allow scripts to run. A little window will pop up which allows you to put in the URL for the picture you want to insert, and then for alternate test for the image.
Same thing with a link, use the button, add the link, hit enter. Then add the text you want for the link, then hit the /link button to close.
Blockquotes are the same thing. Hit the quote button, enter your test, then click on the same button which has changed to the close blockquote button.
In comments, you’ll want to add some sort of text before the HTML code, otherwise the code ends up in the subject line.
By the way, there is lot of info here