In current 1.19-svn trunk, edit summaries for page edits are not shown on Special:RecentChanges.
Summaries are shown for page moves, uploads and imports, but not any edits. Even auto-summaries (such as section edits) are not shown. Summaries do appear on diffs, so work on input and are in the db. They're completely missing from HTML, not just invisible.
Tested on different 1.19-svn installations, without extensions, using different skins. Not aware of any feature changes that say this should have been removed.