People get confused because the term concealment has several definitions/uses. For example, a completely invisible enemy has 50% concealment even if you know which square they are in (from a successful Listen check, for example). This is, of course, not the same as concealment from obscuring terrain, which is typically 20%. Nor is it the same as the total concealment granted by a tower shield if you chose to hide behind it.
DnD 3.x had terminology problems and Pathfinder inherited a lot of it.
So, let's go through the spells one by one (3.5 versions):
See Invisibility negates Invisibility. That is it. Therefore, it will allow you to hit an Invisible creature as though it was visible (no 50% concealment from invisibility). However, if it was obscured by other means, then it will still have the concealment from those means.
Glitterdust and Faerie Fire outlines and marks the enemy. It does not make them visible. Therefore, it negates the 50% invisibility concealment bonus, but it does not allow you to do precision strikes on them (e.g., sneak attacks), which is, unfortunately, another definition of concealment.
True Sight negates Invisibiity, Displacement and illusions. It does not help vs Hide or other non-magic forms of concealment.
If the game does not behave like the above, then there is a bug.
There's nothing in the Glitterdust text that specifies that it counters Concealment...
I get that you said 3.5 but this is a Pathfinder game...
Found a thread here:
https://paizo.com/threads/rzs2s1xo?Glitterdust-vs-Displacement
Consensus seems to be Glitterdust does NOT affect Concealment.
If it reveals an invisible creature, it counters the concealment given by invisibility. I did not think even Paizotards need to be told that.
Except it doesnt, per the spell's written text.
A cloud of golden particles covers everyone and everything in the area, causing creatures to become blinded and visibly outlining invisible things for the duration of the spell. All within the area are covered by the dust, which cannot be removed and continues to sparkle until it fades. Each round at the end of their turn blinded creatures may attempt new saving throws to end the blindness effect.
Any creature covered by the dust takes a -40 penalty on Stealth checks.
The spell specifically references
invisible things, it does not reference Concealment at all.
This means that it outlines invisible objects and allows them to be seen, so it counters
invisibility effects. But it does
not counter effects like Blur and Displacement, here's the Displacement text as an example:
The subject of this spell appears to be about 2 feet away from its true location. The creature benefits from a 50% miss chance as if it had total concealment. Unlike actual total concealment, displacement does not prevent enemies from targeting the creature normally. True seeing reveals its true location and negates the miss chance.
Displacement is an Illusion spell that makes the creature appear in a slightly different place to where it actually is, thus Glitterdust has no effect because the glittery dust that the spell releases is also shifted visually by the Displacement spell.
That's why Glitterdust specifically fails to mention Concealment.
Glitterdust counters invisibility and whatever miss chance such invisibility might grant, but it doesn't counter Concealment directly. If it did, it would say on the spell text 'Counters all concealment', like the Faerie Fire spell does:
A pale glow surrounds and outlines the subjects. Outlined subjects shed light as candles. Creatures outlined by faerie fire take a -20 penalty on all Stealth checks. Outlined creatures do not benefit from the concealment normally provided by darkness (though a 2nd-level or higher magical darkness effect functions normally), blur, displacement, invisibility, or similar effects. The light is too dim to have any special effect on undead or dark-dwelling creatures vulnerable to light.
