The RTFM warns that this may be problematic if the inner placeholder tags are processed before the containing snippet is processed; it recommends to only use such a syntax in Property Sets. That said, I've never had a problem using @CODE in the same manner - I've never used @INLINE.
Also, be aware that the example shown in the RTFM is using quote marks to deliniate the sample, when actually used in snippet properties it must be backticks.
This must be followed by a space, e.g. "@INLINE <li>[[+pagetitle]]</li>"
In actual usage, that would need to be
`@INLINE <li>[[+pagetitle]]</li>`