The Kunena team has announce the arrival of Kunena 6.2.1 [K 6.2.1] which is now available for download as a native Joomla extension for J! 4.3.x/4.4.x/5.0.x. This version addresses most of the issues that were discovered in K 6.1.0 and issues discovered during the last development stages of K 6.1
1/ Create a new post or reply.
2/ Switch to Source editing
3/ enter: [/quote]
4/ post the message. It appears as "[/quote]"
5/ When edited, the edit box is empty, and the Source button is disabled.
This is a known error in the CKEditor. This error occurs when you have wrong or incomplete BBCodes in the message. In your case, the message contains two "quote" end tags and the first code tag without slash for each of these codes is missing.
This is one of the reasons why we copied the old BBCode editor back.
Go to your Kunena template setting (tab BBCode) and choose the BBCode editor. Then you can edit these messages.