My experiments in fixing that have led to the "Save" Talent/Stat Points addon. The idea is that you can now right-click on the level-up marker to mark your current unspent points as "saved". If you have saved points but no unsaved points, you'll get a distinct level-up marker:

(The Minimalist UI isn't a particularly easy UISet to override bits of, so what I can do here is kind of limited...) As you can see here, saved points are tracked separately for each party member.
This is a work in progress, of course, so I welcome suggestions for improvement.
[edit 2013-11-12 11:58pm: Technical info:]
Code: Select all
Superload:
mod.class.uiset.Minimalist:
displayPlayer() [to apply our "saved" points indicator]
displayParty() [to add "saved" points indicators to party icons]
mod.dialogs.LevelupDialog:
createDisplay() [to hijack the top buttons as 'save-points' buttons]
onUseTalent() [to update the button labels]