This very simple simple modification will allow you to replace the "post new thread" button text on a per forum basis. The page title on the create thread page itself is also amended.
1. If you have an "introductions" forum.... you can change the "Post New Thread" button text to "Post New Introduction"
2. If you have a "news" forum, you could change the button text to "Add News"
I've not included screenshots because I think this is all self explanatory.
To set the button text, just edit a node - you'll find the extra option under the node description.
This mod displays no branding, there are no callbacks, it adds no queries and it's free - however, if you wish to make a donation then just PM me.
If nothing else, then at least leave a review