Additional info/insight: Once I'm on the forum and a new post is made, the yellow icon will appear in the active topics for that post. As additional new posts are made in that session, each has a yellow icon.
If I leave (close the browser) without reading any of the new posts (yellow arrow icons still present), then return (start another browser session), the yellow arrow icons disappear in the active topic display. New post indicators are still present at the forum (yellow folder) and thread ("new" icon) levels.
