Is there any way to change the name of threads manually?
Sure. Just move to the very first posting of the topic, hit “Edit” and change the headline.
This is possible in most forum categories, but not in “Play Boardgames” where edits are never allowed. So type carefully there ;-) . However, you can ask a moderator by pm to edit the title, there.
In that case it is important to send the link to the respective topic and what you want to have corrected there.
You know Angelina Jolie had a flying submarine in Sky Captain.
Keep him a sub just let his post count keep climbing. It is the post count you look at to see if someone is a regular poster (to my way of thought) not the “rank.”