Hi @stevenzhu,
I don’t see anything inappropriate about using Let’s Encrypt certificates for e-commerce. Lots of e-commerce sites already do use them. While using a paid certificate may help show that one has money to spend on infrastructure (which might be a useful signal to some customers), and using an EV certificate could help motivated customers confirm the seller’s legal identity (which a few customers might appreciate), the quality of the encryption and authentication will be the same, and Let’s Encrypt certificates can be used in PCI-compliant applications, for instance.
I agree that if your hosting provider doesn’t directly support Let’s Encrypt in an automated way, it might be more convenient to obtain a longer-lasting certificate than Let’s Encrypt offers, in order to avoid the inconvenience of forgetting to renew.