I don’t necessarily disagree with your arguments, but this topic really saddens me. Choosing CAs because of their names rather than… anything relevant to security or usability?
More objective cents from me:
Let’s Encrypt does not provide site seals since, whether or not they are profitable, they do not convey trust.
Respinning the intermediates with a different name would be a pretty massive hassle.
On the other hand, Let’s Encrypt is scheduled to create ECDSA roots and intermediates eventually, so they could be named something else, and it would be somewhat less of a hassle to generate new RSA intermediates then.
There was actually a recent case of some old server software that did not support certificates with ’ in the name.
Totally rebranding Let’s Encrypt at this late date sounds like a massive hassle, and extremely counterproductive, since the existing name is already well known.
Rebranding the certificates would probably cause more trouble than it’s worth. We would get a lot of confused users who want to know what in the world an ISRG is and why they don’t have a Let’s Encrypt certificate.
Many of these things could be studied and quantified – at significant cost – but I’m just saying things.
Let’s Encrypt is a non-profit with the goal of increasing Internet security, not a corporation pursuing 100% market share. It’s not actually bad if people use other CAs.