I consider the wiki critical to the survival of jmonkey myself so I took up the cause.
Yes. Anyone who gets the urge can contribute.
Removing pages is not something that's currently done because the wiki covers more than one version. Ideally, a new wiki would follow each release but that requires a team dedicated solely to that purpose, just like the core team for the engine.
Documentation is tedious, requires a more intimate knowledge of the engine than most users have and expects you to learn a new language to contribute. There's no glory in it either so this all leads to less interest in contributing.
The wiki can use style sheets to make it snazzy but its not a priority at the moment.
The syntax usage requirement wouldn't change. How its presented could be. Using Mark Down for documentation is a no brainer once you understand what it does and how to use it.
Its up to the project creator to document there own projects and if a project is not an official part of jmonkey it will at best usually just get a link to it somewhere unless someone takes up the cause and writes a tutorial for it.
That's slowly going to change.
This looks to be a conversion problem to me.
Just a guess but...
The wiki used to be stored on World Press and I'm not certain but it may be that a font was used to place the smart quotes directly into the text and World Press recognized it as such without any special formatting instructions. When converting to AsciiDoctor, smart quotes use back ticks enclosed by quotation marks to format text so instead of striping out the problematic smart quote, it leaves half of it there to let you know there is a problem with the formatting.
When I first came to jmonkey it had just changed over to using AsciiDoctor and was nearly unreadable with outdated info, broken links and significant formatting problems. The wiki is over 500 pages and I had to prioritize what to fix immediately while learning how to use AsciiDoctor and the jmonkey engine so the most obvious thing was to try and fix all broken links first, then formatting, then content. I felt it would be best to fix 10 pages of broken links in a day rather than one or two pages completely.
Smart quotes didn't and do not even hit my radar screen to sum it up.
Feel free to fix them though, you can find the original wiki using
so you can figure out what the original authors intent was. Its important to keep that in mind when editing. They spent the effort to write the pages so respect their efforts..
The best is Archive.org. which gives a calendar of dates to chose from. Drilling down will produce results like this,
so you can navigate the documentation.