The current method that requires double-clicking to start editing the contents of a table cell is neither normal nor intuitive. Please add a tooltip, so that when the user hovers over a cell, s/he'll discover that double-clicking is necessary.
Related ideas from Thyrduulf on the general subject of reducing this confusion:
"There could be a menu icon that is activated when a table cell is selected (single click) which you click to open the cell for editing. The latter will be more work but might be more accessible. Another option would be a dismissable dialog when a table cell is selected (single click) that says the same as the tooltip - this would get very annoying though and a "don't show this again" option would be essential."
I don't know whether it is normal or not in other editors, but it is distinctly non-intuitive in the context of editing wikis. I'm a very experienced editor and have a higher degree of computer literacy than many users, and it took me a few minutes to work out that I needed to double click to edit the contents of a table cell.
Some sort of indication of what you need to do is essential here, and tooltip when hovering over a table cell is how I'd expect to be informed of this, either with or without a menu button that was highlighted. A dialog box is also not incompattible with either, and would be of most benefit to those who are not so comfortable with looking for more subtle cues - exactly the sort of user I thought VE was intended to assist.