Nachdem ich meine Joomlainstallation upgedated habe, lief jcomments nicht mehr vernünftig. Nach kurzem googlen fand ich die folgende Lösung:
Im Joomlatune-Forum beschreibt BobCraven die Vorgehensweise, um jcomments wieder vollständig zum Laufen zu bekommen.
The changes from 1.5.9 -> 1.5.11 (and probably also already in 1.5.10) are in components/com_content/views/featured/view.html.php and in components/com_content/views/category/view.html.php. De context is now 'com_content.featured' (lines 79-91) and 'com_content.category' (lines 99-111). The context before was, in both cases, 'com_content.article'.
I fixed this issue in JComments by changing lines 289 and 327 in the plugin (plugins/content/jcomments/jcomments.php)like this:
if ($context == 'com_content.article') { ...
replace by:
if ($context == 'com_content.article' || $context == 'com_content.featured' || $context == 'com_content.category') { ...
Danke an Inge und BobCraven...