Hey Growmie,
Currently, GrowDiaries doesn't support direct replies to comments due to the craziness that use to happen on the site. This limitation arose after a site update that disrupted the previous comment system. As a workaround, users often post a new comment or question referencing the original commenter. Alternatively, you can send a private message (DM) by clicking the paper airplane icon in the bottom right corner of the screen. This method allows for more direct communication with fellow growers. As far as for the shorts just upload it to your diary and the site will take care of the rest.