I figured these would be better placed here than where they originally were, which was in the discussion on the syntax documentation page. I may well add more later, if I can think of anything.
Broadly speaking, BTW, I'm very fond of Wikidot and I think you're doing a great job. I wouldn't nitpick if I didn't like it here ;p
Table of Contents: Custom Levels
How about making it possible to specify how many levels of headings the table of contents lists? For example, to create a document with four levels of headings, but to make the ToC include only three levels?
Table of Contents: Ignore Tabview
When using tabview, it's very unfortunate that the table of contents displays all the headings from every tab as if they weren't separated by the tab layout. More so because clicking on those headings in the ToC doesn't change the active tab. Adjusting tabview/ToC to solve this, if possible, would make tabview much more attractive.
Lists: Multiple Sub-lists
<edit: Nevermind, this seems to be working fine. I wonder what happened when I first tried it? ^^;>
Tags: Unlimited Characters
The tag system is pretty satisfying in general, but it's sorely disappointing that the number of characters is so limited. Right from the start, I didn't have enough space to tag my pages with all the tags I wanted to sort them by; the more content my wikis get, the more I need to abbreviate the tags to fit them all in. The tags feature would be much better if the limit were removed entirely.