So, as many of the more frequent Wikia editors know, there are two modes for editing: Source Mode and Visual Mode. The basic idea is that Source Mode includes all of the HRML formatting while Visual Mode renders such formatting as small icons. Source is known for being a bit more code-heavy, what with template formatting and all. Visual is known for doing things that editors are not necessarily trying to do.
While Visual Mode can be useful for newer editors who aren't used to Wiki-markup of any sort, this mode has a tendency to, well, mess up how pages are formatted. In Visual Mode, it's much easier to accidentally delete a whole template or set of HTML formatting as such sections are rendered as a small icon (i.e. a puzzle piece for templates). Visual Mode also has a tendency to randomly insert HTML-based text formatting which doesn't actually change anything from the default. Visual also poses problems with editing article links, such that the actual link, itself, is not changed in the process (this poses issues for when someone needs to change the actual article link). The link also, in many cases, is strangely shifted to include adjacent words in the link as well.
I will say, when Visual Mode decides to data-puke on large edits, the clean-up process can become a bit lengthy. Many of these data-pukes make Source Mode editing become a bit more difficult due to random and unnecessary formatting inserts as well as mucking up article links.
Many other wikis have run into similar problems and have requested that Visual Mode be turned off universally for that particular wiki (so that no user of that wiki can access Visual Mode). My question is… do we want to join these wikis in requesting that Visual Mode be disabled, or are more users more comfortable with the Visual Editor?
I've completely stopped using Visual Mode as it's way too unpredictable. It was handy when I first started editiing but after finding that it had a tendency to 'glitch' pages up, I switched to Source to save having to go back and correct whatever it had decided to delete, re-arrange and so on.
My theory is that Visual is very probably possessed - and an exorcism is needed. :p
I almost always use source mode be it a paragraph of text or a gallery. It is however needed for editing the infobox. I know some users prefer to copy and paste source from one page to another in order to make source easier but in doing so, there are often odd flaws. But the real deal is - should we keep it?
I say we should. Although it can be a massive pain, it is still useful in some respects.
The main question I'd have, though, is whether there's really anything that Visual can do that Source cannot, or if there's anything that's really more useful. Especially if most / all editors use Source and not Visual, there really wouldn't be much reason to keep Visual Mode.
Particularly with large edits, Visual mode tends to introduce so many errors that clean-up requires re-writing almost the whole article. What Visual seems to do is force the page to insert formatting code or add that annoying   all over. If the user so much as selects or clicks on the text, Visual mode may add all sorts of wonky formatting. In some instances, it goes so far as to break the whole article page, though that is a fairly rare case.
I've also seen a lot of instances where users will try to edit a link while in source mode. Unbeknownst to the editor, they're not actually changing the link. So when it doesn't work, the editor tries, sometimes a number of times, to correct the link.
Probably one advantage to Source over Visual is that Source shows all of the coding for an Infobox or other template instead of a puzzle-piece icon. If I were a new editor to a Wiki, I would recognize that the template-code is something I didn't understand and thus should avoid modifying. I would be more likely to remove the puzzle-piece either by accident or because it looks like it's an error.
At least from what I've seen, the main issue with the Visual editor deals with new editors who don't know what they're doing (or who attempt to edit an Infobox and end up removing the whole template).