Is the difference that drastic?

Short version: Yes.

Long version: Writing quality can be meaningfully compared along many axes. There are mechanical axes, like correct grammar usage, clarity of expression, precision, succinctness, and readability, all of which I found to be problems (to varying degrees) with this post. These are all (relatively) easy to improve by proof-reading, making multiple drafts, and/or asking others for editing help. Wei Dai's post performs well by all of those measurements.

There are also content axes, like originality, rigor, cleverness, evidentiary support, and usefulness. Hacking the CEV for Fun and Profit does pretty well by these measures, too. This post is a little better with content than it is with mechanics, but poor mechanics obscure content and dilute its weight, so I suspect that the points you were trying to make were underevalued, though not drastically so. Fixing up content is harder than fixing up mechanics; for some ideas, it is impossible. After all, some ideas are just wrong or useless (though this is usually far from obvious).

One writing technique I like and don't use enough: come up with lots of ideas and only explore the most promising ones. Or, as it is written in the Book of Yudkowsky, hold off on proposing solutions.