How can I add number of user posts in each category to her/his profile?
Adding activities per category to user profile; Does it need a plugin or it can be done by theme manipulation?
Number of posts is an exceedingly poor metric for someone’s participation in a community; it measures how much they talk, rather than how well.
While per-category stats may be added in the future, that feature requires some design work to be done well. I strongly object to anything that makes post count more prominent on the profile.