Interesting... I wonder if it's not actually supposed to be a link? I noticed if you hover over mine (for example) it shows my channel username, but if you right click there isn't actually a link of any kind there.
It'd certainly be a cool feature to have it redirect! Along with the discord / twitter / etc ones
This is an external add-on that is not included as standard in the forum software. I did go and edit the template to make it link but then I realized why it was not implemented in the first place.
YouTube channel URLs do not always correspond to the channel name because you need a certain number of subscribers and other parameters to be met to be able to set a custom url. So using a template youtube.com/[channel name] won't actually work for most people's channels.