Which one is right?

I'm almost completely self-taught, and I don't think either one is "wrong"... I prefer the second version; perhaps someone who is schooled in grammar can tell us exactly why.

Yes, 2 is better.
This is because the tense "has reversed" / "has objected" (the name of this tense escapes me just now) indicates that the action referred to happened in the past but has consequences in the present. In this case, it seems most likely that it is the more recent action - the action that "sources" are bothering to tell us about - that is the one that is more important and has most impact on the speaker/reader.

Also acceptable would be "In some cases, the sources said, Hu reversed himself after Jiang objected to a decision."

Hi Wy and Eos,

Eos, did you mean that "sources" emphasized "Hu reversed...", so the present perfect tense has been used there?

In addition, regarding your sentence "...that the action referred to happened in the past but has consequences in the present", it seems to me that I am so unfamiliar with "to" followed by the past tense of a verb. Grammatically speaking, I think we could use "happening" there. But hey, I felt using "happened" looks exactly logical. Hmm, a bit of dilemma aroused.

#1 would be fine if "has objected" were changed to "had objected". Since "reversed" is past tense, if it is followed by perfect tense it should be past perfect not present perfect.

#2 would be better if the "has" were removed making the entire sentence simple past tense.

Sorry to cause confusion - you misunderstood. When I said "the action referred to happened in the past but has consequences in the present" - you should understand that 'the action referred to' is the entire subject of that clause. As in 'the action that is referred to in the sentence'. The 'to' belongs with the word 'referred' - not with 'happened'.

There's no such thing as 'to happened'. You can't make any form of a verb with to and a past tense.

Absolutely clear now. I should not make such a mistake on so simple question.

No problem. It's a blasted difficult language. I sympathize with anyone tackling it as a second tongue.