So if a player wanted to stand, spending the move action, but not moving because its not leaving the adjacent square. Does this meet the requirements for ending the ongoing damage?
No, it doesn't meet the requirement for ending the ongoing damage. The description for Reaving Damage you quoted says the following:
that enemy also takes ongoing 5 damage until it spends a move action (without moving) to end the ongoing damage.
A creature under the effect of Reaving Ammunition takes damage not until it moves, but until it spends a move action ending the effect.
That means your player needs to expend their move action completely on simply ending the ongoing damage. If they want to also stand up, or run around, or engage in any other form of move action, that requires a different move action. They do not get to end the ongoing damage as a side effect of performing a move action.
You appear to be confusing the concept of a move action with movement.
On Actions available
As you may know, in your turn, you get to perform one of each of these actions in any order:
- A standard action
- A move action, and
- A minor action.
If you're not so familiar with this, the Rules Compendium talks about these on page 28, and the Player's Handbook talks about these on page 266 (I think - I don't have my books with me at present).
As those pages describe, you can also trade them downwards in that order: a standard action can be spent on a move or minor action instead, and a move action can be spent on a minor action.
What this means for Reaving Ammunition
Normally you'll use your move action to perform movement - to run, stand up, shift, or a few other kinds of actions. If you want to run up to your target and attack them with a power, that probably requires a move action (to run up) and then a standard action (to use your power). That leaves you with a minor action spare for various effects (e.g. sustaining a power).
In the case of Reaving Ammunition, a creature spends its move action on ending the Reaving Ammunition effect instead of using that move action for movement. This sucks for your target, because now they're in a tricky situation. If they want to end your Reaving Ammunition's effect, then in that same turn, they won't be able to move and attack - they will only be able to do one or the other. If they want to be able to both move and attack, they have to continue taking Reaving Ammunition's ongoing damage.
The only way to move, attack, and end Reaving Ammunition's effect would be to use up a precious action point in doing so - if they even had any available to begin with.
Reaving Ammunition puts your target in a tricky situation and leaves them having to make a difficult choice about what resource they want to waste each turn until they end the effect: precious health, precious actions, or precious action points.