How do you reckon a 3rd party battery can damage a camera? If the output voltage is correct (which is not difficult to get right), a battery is just a simple device that should in theory and practical, not damage any electrical devices, unless you are a marketeer who wants your customers to purchase your over-priced piece of accessory, hence spreading half-truth, fears and rumours etc.
As you said you have past experience, I would be interested to know what it is? I have been playing with various type of lithium batteries, not to mention those with LiFePo4 or NiMh chemistry as well for over 10 years. While I can never claim to be even close to be fully knowledgeable in all things battery related, I do have sufficient experience in handling them and have not seen any batteries damages another device unless you are talking about battery leakages or you are using one with an incorrect output voltage (which should be 3.6V for your camera) or purchased one with bad manufacturing quality. But in general a properly sourced lithium battery should not damage a device. Just because they are no brand or labeled "Made in China" does not mean they are not good as I have seen many 3rd party manufacturers often produces better quality batteries than the OEM (which are also Made in China). User just need to purchase a third party battery from a "safe" and "reputable" source and you should be alright. Of course, for many buying OEM will be the safest (and most expensive) but I think a broad brushstroke generalisation of 3rd party batteries is very far from the truth, because your camera maker do not produces his own batteries and they contracted it to a battery manufacturer in China to OEM for them.
*Just to be upfront, I'm just a hobbyist and a consumer, and I have no vested interest in any trade or sales of batteries, OEM or otherwise.
Output voltage is only part of the equation.
1. Material used, are they really as listed in the spec list?
2. Cost is so much lower, so how can the cost of same material be so much different?
3. Production... are you sure those company have R&D to ensure the Battery to operate to the spec of the Manufacturer?
4. Capacity.... some battery are so much higher capacity... but how is the discharge?
5. Do you measure the output voltage and that there's no surge? Is it stable throughout all operating temperature?
I have 400D 3rd party cos I cannot buy original cos not in production, and the battery charges does not hold... so talking about QC...
I use a sony video cam after using with third party camera, start to functioning weirdly, and we got a high capacity battery, but after using with it, the function is weird, and brought in for servicing.
You never heard of exploding batteries in handphone? For Apple, even original batt can have such incident, so not to mention 3rd party. Oh... I think they used 3rd party charger... but that screwed up the battery, and phone circuit get short circuit...
Battery is the source of power for the Camera. It is simple, but one of the most important. It is not as simple as some people think it is. What is happening in a battery?
A cycle of process is happening, in which, Chemical process take place, and corrosion happens to produce electrical energy. Battery also leak, and the leakage can damaged the electrical component.
If I have money to buy a $2000 camera, I will budget $100 for extra battery. Not worth to risk damages to the camera.