No its not wrong to get wound up over that...I definitely would.

If anything I'm probably more wrong than you - I get bent out of shape when SO talks to BM about Princess SS7, cuz it's always "oh did you see he had a bruise on his leg...hey do you think he has chicken pox (it was a freaking heat rash, those little bumps around the sideburn and jaw area TINY LITTLE BUMPS and they were about to take him to ER cuz they thought it was CHICKEN POX)...or hey what time did he sleep last night, cuz he's so tired he fell asleep in the car after school...or hey did he eat enough dinner last night cuz he really ate a lot today...or hey do you have his jacket, its his favorite one and he wants to wear it tomorrow..." And this is me in the background - OMG he sneezed, I think he's dying.

I could go on, but I think you get me drift. I want them to shut up already.

Is it wrong? No. Is it necessary? No.

If my SS's ex (SGS's BM) discussed vehicle accident/buying a new car my first thought would be, 'why, did she crash her broom stick?'. But anyway....the only time he ever talks to her is pick-up/drop-off in person. When he has to discuss SS it is all done by email.

In reality a five minute civil conversation (even if not necessary) is pretty harmless enough unless BM is leaning on the guy for real advise and support. It's not your DH anymore, BM. Civil and generic is better than rude or a fight fest, especially in front of the kiddos. But still, one has to wonder why? Gossip? What's to gossip about with an ex? If the talk isn't about your children, why stand around and chat like old friends?

I can see both sides of this argument.

He may have shown interest in it solely because she will be transporting his kid in the new car.

If it happens all the time, discussing things in general, then yes you definitely have a beef. Their conversations should be limited to your skid and important items that may pertain to her.

If it's just once in a while and over things that may not be about your skid, but will affect your skid, then I'd probably overlook it.

Bm does this crap too,totally attention seeking and unnecessary. Dh needs to learn some damn boundaries. Unless it is about sd,it needs to be ignored. That is not being rude,it's drawing the line. Bm infuriates me with her pathetic behavior.

No, not wrong. I'd freak out, personally and make it end.

They probably shared several years together and it takes time to disengage entirely.
My ex will still ask for advice about something I know more about than him. He recently asked me how my grandmother rooted African violet leaves. Now we have been divorced over 10 years and why he couldn't look it up on line I don't know. But he asked and I told him.

Now if they are having coffee meetings and she wants him to go car shopping with her... no go. But if she is showing him pictures of her damaged/trashed car he probably (being a bloke) finds it interesting.

What I learnt is that if you make a fuss about it it makes you the nutcase. When he comes inside be extra nice to him and give him every reason to hang around with you more than her.