You could check before you open the message thread.
Yes, you could. But that value can change behind the scenes without your knowledge. How often are you to keep checking other places (always loading screenfuls of information you don't want, creating more network traffic and server load) instead of just glancing up, as you can with most other types of currency.
I can't see why anyone who thinks about it, doesn't wonder why it hasn't been there already, for many years.
What is requested in FoE helper is totally irrelevant. Discuss that on their forum.
It is not irrelevant. It is a feature wanted on FoE, and shown to be popular in 3rd party software (which Inno discourage the use of).
The popularity of features in third-party software is clearly not an irrelevance: it is a simple (and cheap) way for Inno to know what users really would like. They certainly seemed to have taken notice of the growing trend of alternate noticeboards and are bringing out an improved message centre, for example.