Thread:VisualEditor/Feedback/Unable to add my signature via VisualEditor/reply

This is intentional – the editing experience for a rich document editor and a rich comment editor are somewhat different, and rather than try to build a hybrid editor that serves both needs poorly, VisualEditor is focussed purely on the first. Flow, which will use VE's editing tools in time, is the project to make talk spaces great. As you mention, there are a number of different areas where users are encouraged to sign their name, and all of these will (in time) be served by Flow; this is why (for example) VisualEditor is disabled on the Project: namespace on most wikis.