This sentence sounds like it’s intended to be spoken in English.

The use of progressive might sound unnatural. What is the idea of using simple words?

He is reading articles which he summarizes in his blog. (I prefer that) He’s

reading articles, (that or which) he’ll summarize in his blog. (He’s reading his blog). This version is better

if you are only talking about that action in isolation.

Your relative clause is not-defining, so it requires a comma.

What is the meaning of your alternative version? The articles that he summarizes do now appear in his blog that the relative clause has become a defining relative clause.

I agree with you. Your sentence sounds like it’s awkward and unnatural even with my suggested correction and would only sound okay in a

context. Please reconsider.