This bug occurs when replying to a post by selecting the "reply with quote" option.

It's impossible to insert a paragraph of your own at the top of your post, before the quoted text. Every time you click the blockquote icon to remove the quoting on the new text, it adds one more level of recursive quoting to the original text.

It's hard to descibe, but if you try it it's obvious what the problem is.

Another, possibly related, issue with quoting is that some actions cause the text to separate into indivual blocks. So, for example, you end up with:

xyz said:

hello world