Okay, so I have two triggers for rebounding, in case someone's name gets long:

For the two-line:
#TRIGGER {You suddenly perceive the vague outline of an aura of rebounding around} {}
#COND {(%w).} {#echo %1's rebounding up!} {within|param=1}

Just one:
#TRIGGER {You suddenly perceive the vague outline of an aura of rebounding around (%w).} {#echo %1's rebounding up!}

So, when I see someone's rebounding up (someone with a short name, so it's the one-line), I get:

You suddenly perceive the vague outline of an aura of rebounding around Person.
Person's rebounding up.
up's rebounding up!

I figure this has something to do with one trigger activating on the other, but I'm not sure how to fix it. Help?

Try tacking on an end-of-line character ($) to the first state of your first trigger. That will keep it from triggering on both cases and giving you the extra echo.

There might be some mismatch between the output given and the triggers given. From the output (quoted below), the second (1-state) trigger was actually doing this:
#echo %1's rebounding up. (ending with a ".", not a "!").
This would cause the first (2-state) trigger to fire, resulting in:



So changing the second (1-state) trigger to "#echo %1's rebounding up!", as shown in your post, should fix this.

Another quick fix is to change the first (2-state) trigger to:


Or, if you want to combine these into 1 trigger, you can grab the "You suddenly perceive" line plus the succeeding line, then parse the person's name out with %regex() like this:

This uses some extra variables though, so you might prefer to stay with two triggers instead.

I didn't test that code by the way, so the syntax might be slightly off.