I thought she asked him to buy the tickets. I thought that was weird, since she’d been shopping, and may still have the window open to make the purchase. But i also thought the ask was unambiguous.
This impresses me as the type of miscommunication that often occurs with texts. People intentionally use shorthand, and raise/drop various issues such that the conversation does not progress in a clear, logical, linear fashion.
I think there was enough ambiguity at the point that she said, “Go ahead and buy tickets”, that it was not unreasonable for you to check to make sure you were both on the same page. IMO, any conceivable transgression on your part is greatly outweighed by the potential harm from miscommunication: either you BOTH buy tickets, or neither of you do. At that point, even if she thinks you were being dense, all she had to respond is “You.” Or maybe “You, please.”
Instead, she got pissy with her next text - and in the process did not clarify your uncertainty.
Then you built upon her pissiness by bringing up punctuation. Did you really think that was going to lead to any good resolution? How many times does one spouse piss the other off - intentionally or not - when the proper response is to simply let it pass and move on. At that point, you should have simply responded, “Thanks. I’m buying the tickets.”
Maybe later you could discuss your texting practices IN PERSON. BEING CAREFUL TO NOT PHRASE IT IN A CRITICAL OR SCORE-KEEPING MANNER. Simply apologize for any confusion you entered into the conversation, and asking how either/both of you could avoid such confusion in the future.
I feel like y’all are focusing on the wrong thing. Yes, it’s true, “Go ahead and by tickets” is not ambiguous. And yes, I’m not sure why the OP is focusing on punctuation there. However, I would have responded exactly the same way (Wait, am I buying the tickets?) and would have been annoyed at the response (Is this a trick question?)
Let’s come up with an analogy:
Her: “Do you want steak and lobster for dinner tonight?”
Him: “Sure!”
Her: “Great, let me see if there’s any deals at the grocery store.”
[later]
Her: “No deals, go ahead and buy everything and make dinner for us.”
Like, she initiated the conversation, she did the research, she may have had seats picked out… why would he be expected to suddenly pick up and carry out her plan? Is he her assistant?
No, I refuse to agree with reply, and why are you telling me to do so?
Seems like the real takeaway from this thread is “event tickets should have a 24-hour ‘cooling off’ period like airline tickets.”
From my other half, just a few minutes ago… this text: “I have to be there at 515 so will leave here at 430 to get to you x”
Be where, leave from where, what’s happening….. and are those times? (of course they are, but I am pedantic!) so confusing 
That was my reaction too. When one of you has already checked out SeatGeek and knows what seats she can buy for how much and that those seats are OK with her, what’s the point of the other spouse duplicating that effort?
Well, I’ve learned not to text with most of you. I’ve sent texts like:
ETS 1125 ETA 11:25
And
I made out on the plane i made it onto the plane
And been understood. Although my husband did reply to that second one, “with whom?” 
I love you period
And do you love me question mark
Please, please exclamation point
I want to hold you in parentheses
ETA: The song is from the early 1990s, so it all but predates texting.
And another from before that:
What makes it unambiguous is that she told him to buy parking. I do agree, it sounds like she had purchase open, so why ask him?
Maybe her account was low and she wanted him to use his(?)
Not just in a marriage, ALL communications. And MORE from their point of view than from your own (you already know what you mean, I presume).
I spent a large part of my career composing written instructions for non-technical users or our systems, and was constantly revising them to make sure that everything was clear from their point of view. That skill has proved useful in the rest of my life as well. I have a friend who never does that, is always throwing out non sequiturs or changing the focus of the conversation without notice or preparation, and it drives me nuts.
I had a good text ambiguity today.
I have a pilot friend who I’ve known for 30 years. We phone every 2-3 weeks and yak for an hour-ish. Usually it takes a couple of texts to set up an approximate time to call, often tomorrow morning. Due to both our travel schedules, right now today we’re a couple weeks behind on our call. We’re both very used to coordinating schedule stuff; kinda an occupational requirement.
So at about 10am today our txt convo goes like this:
Him: Are you home from travels?
Me: Yes, a few days ago. Can’t yak now. How about >1300 today or <1000 tomorrow?
Him: Talk to you then!
Me: Which then?
… no response …
Around 1300 my phone rings. Of course I’m running late based on his norm of tomorrow morning being the answer that fits his life. So we don’t actually talk then. We do an hour later after another round of less-ambiguous txts.
Read for comprehension people. And write for both parties’ context, not just your own.
She found the tix, now why is she telling you buy them, and is parking optional? But only if you want
Now she’s snapping at your request for clarification
Clocks ticking grab the tickets!
For crying out loud, does anyone actually talk anymore? every one of these ambiguous texts could have been solved by actually talking.
My feelings exactly. But many people eschew talking on the phone. Drives me nuts.
Often a 60-second conversation can prevent numerous ambiguous back-and-forth texts (and emails, for that matter).
I run into this with ski trip organizers as well. They never call you back. Everything is text, WhatsApp, or email. I get that they are dealing with many people, but if you’re going to commit to running a trip (and benefitting from the free or discounted trip for yourself), you should also be willing to talk to people on the phone!
At least most people still answer the phone at work (or return calls if they’re busy).
I have a speech impediment. Talking is never my first choice to communicate.
Then again I’m not organizing group trips or sales teams.
I would prefer to have the information in writing.
That’s why, especially at work, I follow up phone calls with an email documenting what was discussed. They invariably start off, “As we discussed on the phone…”