Version: (using KDE KDE 3.5.7) Installed from: SuSE RPMs Bug 1015 (message templates) was recently implemented; however, it seems the only way to access this feature to reply with a template, apart from assigning a shortcut key, is to right-click on a message and select "Reply with custom template" from the context menu. Please add "Reply with custom template" to the Message pull-down menu next to the other Reply commands ("Reply", "Reply to all", "Reply special").
This seems to be fixed in SVN trunk, where the templates are also in the message menu (of the menubar).