Yes - because instead of a "reply" button there is a "locked" button. I have encountered it too when researching an issue on this Opera forum:
https://forums.opera.com/topic/12496/search-engine-keeps-switching-to-yahoo
I wanted to add my solution to this conversation but it is not possible to reply. Why is that? I am quite new to these forums, why is there a lock? Is it done by the person who started the thread or is it something else?