How to convert username to hyperlink in comment reply similar to StackExchange? Is there any contributed module or usable functionality which is somewhat similar to StackExchange reply comment, where when we add username with "@" sign, it notifies user. However in my case I would like to convert them into users profile page hyperlink. 

For example, if user added in reply @foobar, if username with foobar exists will be converted in hyperlink to foobar profile page.
You are looking for the Mentions module:


  The Mentions module offers Twitter like functionality, recording all references to a user's username - using the [@username] or [@#uid] filter format - from various locations, providing a centralized page to track all mentions (via the Views module).