It sounds as though you are trying to shut down the thread. It is probably true that people have said much about Brexit, but it's not over yet by a long way.
I also have dictionaries - print and online - so am perfectly capable of looking up the definition of 'sovereignty'. If you have access to academic libraries, you will also find that reams have been written about the concept. As you quite rightly claim, even 'experts' can't agree. It would appear that you are unwilling/unable to give a definition which links with the EU. Ah well!
If you have found FullFact inaccurate, maybe you could give examples. I have used the site in the past and followed the links which it gives. I queried something once, so emailed the site owners. I received a reply within a few days explaining a misunderstanding. A note was subsequently added to the article. Maybe you should do the same, before you rubbish the site.
If you're not interested in further contributions to the thread, it's really not too difficult to avoid it and allowing people who want to discuss further to do so.