Mark as helpful

Not quite sure where to ask this, so I'll try here, Mods please move as appropriate.

If you make a post and someone replies, you can select "Mark as helpful", which gives their post a green background. I have done this a few times to people who have been kind enough to give me good information, but when I next view the thread, the posts I have marked are no longer green.

Any ideas?

They stay green for me, so if you have found a bug please make a Report, being as specific in the details as possible.

Got it. On the first click, the post does go green, but is not get saved as such. A second click produces an icon next to the "Mark as helpful" and it is saved. Paradoxically, once you have marked a post as useful, unmarking it and remarking it only require one click each.