The main problem with more sophisticated RST support is that ikiwiki turns 
preprocessor directives into raw HTML and reST hates inline HTML.
inline relies on Markdown's handling of raw HTML, specifically
that it doesn't wrap paragraph-level `<div>`s in `<p>` tags -- see 
[[todo/htmlvalidation]]. Other plugins might expect their output to be 
interpreted in certain ways too -- [[Joey]] mentions toggleable and fortune.

Is [prest][1] the perl version of the reST processor referred to in the text?
It seems to be reasonably well-maintained to me, and differences between it and
"standard" reST are pretty minor. A fairly exhaustive list, taken from the 
prest docs, follows:

[1]: http://search.cpan.org/~nodine/Text-Restructured-0.003024/

An exhaustive list of differences between prest and "standard" reST follows:

* fewer alternatives for bullet lists (only "+", "*" and "-")
* escaped colons are not allowed in field names
* RCS keyword processing is only activated on "recognized bibliographic 
    field names"
* multiple consecutive blockquotes seperated by attributions may not be allowed 
    (not sure; text could be interpreted either way)
* a warning about auto-symbol footnotes is missing (maybe it's not relevant?)
* colons are allowed within hyperlink reference names
* inline markup can be nested
* some directives are missing (epigraph, highlights, pull quote, date) and 
    some have been added (MathML, code execution (disabled by default), enscript)
* container directive now uses "class" instead of "classes"
* csv directive doesn't require csv.py
* references directive doesn't allow options

There may be a few others; my eyes glazed over. --Ethan