I was watching a VOD (I can't recall which one) and Luminous showed some extra information about skills like range, type of damage and etc. Things that the interface don't really say. I think the text would show in green in the tooltip box like the aghanim's info. He said that pressing 'o' would show that information and that it was very useful, but I went to dota and pressed 'o' and nothing happened. I don't have any commands attached to the 'o' key and I didn't found any option in the controls menu like "show extra info" or something like that. The information the interface provides to you about the skills and the items isn't really that specific to the point of saying if the some abilities have orb effect or can stack with orbs and that kind of stuff. Does anyone knows how to show this information?
In some cases, the AoE/range of a skill will be displayed (centered around your hero) when hovering over the icon with your mouse. You can also view extended information about skills by hitting 'Alt' when hovered over the icon. Green text will appear at the bottom of the tooltip.