Reading thread updates!

Sorry - should have read "that Mumsnet has"

No. Every year, someone from GNHQ starts a thread asking what changes we want. The same half dozen improvements (green OP posts being one of the main ones) are posted by Gransnetters and then studiously ignored. This is repeated each year. Often the requests are for features that Mums that has, so, theoretically, the coding already exists.

It doesn't even happen on my mobile?
Is there something I can do to make it happen?

I don't see the OP's posts in green on any of my devices. (Except the first post in the thread). I wish we could.

I have noticed this phenomenon more recently, too. Several times in the past few days I have wanted to type RTFT, but have refrained. Sometimes posting yet another comment or piece of advice might be helpful for others with the same problem, but sometimes, as you say, it can be upsetting or, at best, frustrating, particularly for the OP.

In some cases it may be that people have opened several threads and read through them one at a time and by the time they get to the fifth or sixth one, someone else has posted something, but the updates don't automatically appear if you leave a thread open for a bit. If this happens to me, and I notice it, I will apologise straight after.

But sometimes the concluding post to the original question is days old, and is just not seen by later posters because it is not green

I don't think this will ever change.