Normally SMF supports that feature but I'm not sure about SMF 1.1.19.
But a 3rd party application may be coded easily.
It works like that;
Get all user posts,
Eliminate all posts whose title starts with RE:
Check the post id on each topic to decide the first post or not.
Voila!
If I've free time I can code something like that.
@bold: I dint get this feature. Will my post ID be reflected or the user's post ID I am searching for? It would be good to have my post ID reflected in the results that appear under "Show new replies to your posts".
Also, is there any suggestion thread where I can suggest new features?
Like the OP wants to search the threads a particular user has created, it would be better if the option is added in an "Advanced" button below the Search bar. One can customize the search results based on the topic created/replied by a particular user or also search the subject of a thread and so on.