After I seeing not much enthusiasm towards this suggestion, I suggest this to be added the way, that you can choose in the ACP between a pre-loaded quick reply editor and a not pre-loaded quick reply editor. I'm positive that this would please everyone
I figured that the TinyMCE editor in "quick reply mode" has its own share of loading time. Whenever someone with posting permission visits a thread, the TinyMCE editor gets pre-loaded. This process takes some time and can even cause lags. You can't expect every user to post in a thread when visited. Many users are just going to read and then leave.
Users would get a more pleasant reading experience if the TinyMCE editor is only loaded when clicking at it. IPB is doing this and in my opinion XenForo should do this too.
That's how the Editor looks in IPB:
And this is how the Editor looks like after clicking at the empty white field:
Please show your support for this as everyone would benefit from a better performance.