It appears that about every other time I click "new posts", the thread titles are listed in a slightly "grayer" colored font, and doesn't seem to highlight threads I've participated in. The thread latest-post-times change to reflect recent entries, so it does appear the query for new posts succeeded...
Clicking "New Posts" again, renders the thread titles in black again, and also the properly highlights threads I've commented in.
Clicking "New Posts" again, renders the thread titles in black again, and also the properly highlights threads I've commented in.