I'd like to find all the messages shared or re-shared by a particular person (me, actually, but it would be nice to know a flexible way) containing (ideally it would be best to include messages bodies, the re-shared messages bodies, links titles and description and comments, but something is better than nothing) a particular word, a phrase or a hashtag. Do you happen to know how to achieve this?
You can search all of the stuff you've posted. Simply perform your search in the Google+ interface, then click the button that says "Everything". That'll open a drop-down menu, wherein one of the options is "From you". That will filter the results to items that you've posted, including shared items.
I don't (yet) see a way to search (only) someone else's posts.