@Karearea - that's the issue!
The 24 hour thing would not be a problem for addicted pruners, as they would be on (several times...) daily, but for some of us life intervenes.
I was assuming it was just me, by the lack of responses, but if you're seeing the same issue it may be PPRuNe.
@IBJoel - it's the 24hr thing that is key - my lengthy exposition was describing the effect (that highlighted threads and 'go to first new post' positioning was screwed up).
Hope that helps. I'm unlikely to be on PPRuNe after tomorrow for a few days as work intervenes, back about Thursday.