The very nature of the adventure makes railroading impossible to prove or disprove. Only one thing ever happens, how can we prove it wasn't what was planned to happen all along? Of course, people have been screaming "THIS IS ALL PRE-DRAWN NOTHING WE SAY MATTERS" since the early ages of drawhores back on /b/.
Most evidence is logic-based or anecdotal, rather than hard proof. Personally I'm convinced beyond all doubt this is done on the fly for a number of reasons:
1. If it's all pre-drawn, why space it out over SIX TO TEN HOURS, AT MIDNIGHT? He could post much, much faster and have to waste less time, and apologists could still just argue he draws fast.
2. Frames that have small changes are posted faster, frames with big changes take longer. Remembering how long each took to draw and then planning an appropriate pause for each one strikes me as more effort than it's worth.
3. I've actually had one of my suggestions used, and I was the only one to suggest it. This could be argued as "I'm the only one who got it 'right'", but then again it's an issue of causality: only one thing happened, and it matched a comment. Did the comment cause the action, or was the action merely waiting for the comment?
It's impossible, by definition, to come up with concrete evidence here, short of Weaver opening some sort of live stream so we can watch him draw while the thread's going.