The ability to write comments in Method Grid, at multiple levels (grid library, individual grids, individual elements) has been in place for awhile.
You have also been able to see in-app notifications (new grids, new elements etc) for some time – see this blog for more on that.
With this new release, comes the ability to @mention a specific colleague to bring a comment to their direct attention.
To use, simply type the “@” symbol followed by the first letters of a name and a dropdown will appear with text-filtered user profiles – simply click on the one you need.