The agent gave you the technically "correct" answer - at least according to policy documents. Car seats are considered contents unless installed with UAS. If you're not the at fault party, then the at-fault person's insurance is responsible for replacing the seats no matter what because their liability covers damage to both the vehicle and property in the vehicle. In that case - when the other person is at fault, it should be replacement cost no matter what.
In the case of you being at fault, assuming you have collision coverage, standard practice is to replace the car seats anyways. In general meloche monnex is very good about seat replacement. I could see room for them to want to give actual cash value (ie, depreciated value,) on the carseats if replaced as part of vehicle equipment because vehicles themselves are treated as actual-cash-value unless you have replacement cost insurance on your vehicle. (Vehicles within a certain age are eligible but it's something you'd have to put on your vehicle at the time of purchase.) But I've never heard of people having difficulty with Meloche Monnex and I know one of the members here who doesn't post actively anymore had 2 collisions in close proximity to each other that weren't her fault, and Meloche paid to have the seats replaced in both cases and then dealt with the other company to get the value of the seats back.
I specifically asked about carseats back when I went through my training when I worked in home and auto insurance and I remember being surprised at the difference in how a carseat could be treated depending on how it was installed. I think in actual practice though adjusters aren't that sticky when it comes to carseats and I kind of suspect that carseats are a bit of an exception - there's "technically" and then there's how insurers seem to handle them. Underwriters are taught the letter of the law because we need to be able to tell somebody whether or not their policy covers a specific event, and from that perspective, a carseat falls in to the contents category unless they are attached to the vehicle, so that would've been the information that the agent gave you. (That's why LATCH is an exception - when attached to UAS, they fall more in to vehicle equipment - and perhaps this is the reason why some people struggle to get replacement cost on their carseats? I've never really thought closely about that aspect before...)
If you're not at fault then it's typically a very easy process and Meloche Monnex is really good for taking care of things directly for you even if you're not at fault - and then they deal with the at-fault person's insurance company for you. Which is really nice in my opinion.
FWIW, the company I used to work for was TD Insurance and they share an office and some office employees with Meloche Monnex. I underwrote home and auto insurance for TD Insurance under primmum. Meloche Monnex policies are underwritten by Security National Insurance. (Right across the aisle of my "pod" was Meloche Monnex employees, and many of the TD employees in our office also held broker licenses so that we could process policy documents for Meloche Monnex when they came in. I know there have been some changes in the company over the years since I went on mat leave (and subsequently quit,) so I'm not sure how all of that lines up anymore, but at any rate, I know that the coverage isn't company specific - it's related to your own provincial standard insurance form. Some provinces have provincial insurers and they have their own policies. I'm not intimately familiar with ON insurance when it comes to auto other than knowing that you have private insurers, so I can't tell you if your policies are fairly close to what ours are here or not, but I can tell you that Meloche is usually pretty good and they train their employees very very well and have a very thorough hiring process - that is, the person who you get on the other end of the phone when you call Meloche either knows exactly what they're talking about or else has somebody there to answer questions for them. :thumbsup:
I can also tell you that while you may have an easier time with some companies than others when it comes to carseat replacement, provinces with private insurers have what is called standard endorsement forms. Insurers can sometimes have their own endorsements approved/customized, but the standard policy - which is what collision/comprehensive/all perils/liability all fall in to, will be the same between all companies within a province. The difference will be how the company deals with you in terms of politeness, speed, and communication. And Meloche comes out pretty high up in terms of their claims process for the most part. :thumbsup:
eta: Sorry this got so long. This is one of those things that is truly just easier to explain in person - I think it took me way more edits and time to try and put this in type in a way that hopefully makes sense when I could've explained it in just a few minutes by voice, lol.