@eleanor*rigby
When I have gotten those html errors in the past, it was usually because I was pasting something that contained hidden html formatting characters. I think that the community posting software will strip them out for you automatically in most cases, but it does generate that warning first. As you indicate, hitting "post" again seems to work, though it can be annoying if you do not notice the error in the mean time.
Not sure if there is a workaround, other than pasting your text into a text box or text document, copying it again from the new location and then pasting it into your post. The google search bar is a handy text box if you have one in your menu bar, but almost any text entry field will do.
If I am copying an entire post, I usually find that if I am careful to start at the first line and end at the last line when selecting the text, I am much less likely to include any formatting characters (which can often cause the text to appear indented when pasted into a new post).
