I find this very useful, but I think the first markup (- haven't tried the second) can interfere with the MarkupExtensions script when it comes to the rendering of anchors.
With MarkupExtensions included after the AbbreviationPlurals markup, any anchors containing strings of uppar case chars are altered by the AbbreviationPlurals script first, which then completely messes up the rendering of the anchors by MarkupExtensions.
However, everything appears to work fine if MarkupExtensions is included before this markup. Probably best, then, to include this markup last.
MarkupExtensions also includes an alternative which requires a WikiWord to include at least 2 lower case characters. So this avoids the whole problem by ignoring strings that are just abbreviation plurals. jr