on 2008.5 when you viewed 'my posts' it used the search, with the syntax 'user:<user number>'. You could then add search terms to that string, and search your posts.
On 7.6, when you view 'my posts' it uses a <username>/my-threads.aspx URL and does not give you the ability to search within the results.
I have tested, and the user:<usernumber> syntax still works in the search engine, but there is no way for users to discover their user number. Is there a syntax available in search for searching by posting user? I know there is the faceted search within a set of results, but it returns very different results than the 'user:<usernumber>' syntax.
Also, is there documentation of all the search syntax, and any differences between what shows up in in the inline results vs the search page?