That's how we interpreted the arrow, so I'm glad I played the mech closer to how it was designed! follow up question: can all my other reactor actions trigger off the same discard? aka can I both load AND gain hp from the card I use to gain height and ascent?
We ordered the triggers pretty true to they way you just described, active then inactive response -- dealers choice on order, but there was some confusion on "do I get my on-hit triggers from my attack before my opponent gets there when-you're-hit triggers," since they seemed like different trigger types, and from context the "when you fire" is on the decision to fire, rather than the resolution of firing.
That makes a lot more sense for the rapière. We interpreted it as "well it says 'move' in the definition for all these other keywords... so I guess you gain X!" (we felt the 30hp mech was very powerful... but then again I also think my friend didn't use radiance or fencing to his full advantage!)
That would be a great distinction to make in the index: when you move, vs an opponent moves you!
My friend and I were very thorough to setup the board and read the rules as exactly as we could.
The market and height slots made finding what we needed decently fast (reminds me of Ticket to Ride!), and the types of cards we needed are very clear on our mechs, but the issue of loading them into our mechs was where I felt the pacing slow down a bit.
You have a really good system to balance out the game per mech. I'm excited to see what you come up with! :)