The most notable article I guess is from South China Morning Post (https://www.scmp.com/news/hong-kong/politics/article/3017530...) and they cite 'a source'.

Also in their article, there are clearly many others in the photographs without masks. So I think his impromptu speech is more important than taking off his mask, but lots of articles cite removal of his mask..

Since this organization has no leader, it would benefit the opposition to paint a leader out of thin air and show faults in him.