There are several ways to link to various things, some can be done just by clicking certain icons in the toolbar while others can be done on-the-fly to help speed things up when your commenting. Here are those commands:
Linking to Users
Shortcut - Adding an @ symbol before an Inkbunny username will produce a click-able icon and username (example: @username)
Point & Click - Highlight the name of the user and click to format it for you.
Name Only - Add [name][/name] before & after their username (example: [name]username[/name]).
Linking to Images
Point & Click - Navigate to the image you want to link to. Copy one of the pre-made links under the image on the right side. Paste that in your comment/message and it will format it into a click-able thumbnail for you.
Shortcut - If the actual submission number is known, just add #S, #M, or #L before the number without spaces (example: #M2340).
Linking Outside of Inkbunny
Special External Links
You can link to users on other major websites such as DeviantArt, Fur Affinity, SoFurry and Weasyl by adding a simple code before their usernames:
DeviantArt - Add "da!" before their DA username and it will make it a click-able link for you (example: da!username).
Fur Affinity - Add "fa!" before their FA username and it will make it a click-able link for you (example: fa!username).
SoFurry - Add "sf!" before their SF username and it will make it a click-able link for you (example: sf!username).
Weasyl - Add "w!" before their Weasyl username and it will make it a click-able link for you (example: w!username).
All Other Links
Copy the URL you want to link to
Highlight the text you want to make into a link
Click (small planet)
Paste your URL into the dialogue box
Click OK, and it should format the link properly for you.