Is it correct/acceptable to leave out the personal pronoun in this case?

Question

Being used to writing in Italian, where using a personal pronoun as the subject of a clause is not mandatory, I wrote the following sentence:

It could be a user thinks the post could make better, doesn't down-vote, but explains what is wrong in the post.

Is it acceptable to avoid writing the personal pronoun in this case?

Are there cases where it is possible, and cases where it is not possible?
For example, I would not find anything strange with a sentence similar to the following one.

I went to the bank to get money from the ATM, bought fruit to Stop'n'Shop, picked up my sister, and went to the cinema.

Answer 1

First, the grammatical errors need to be corrected:

"It could be that a user thinks the post could {be made better / be improved [CHOOSE ONE]}, doesn't down-vote, {but / and [CHOOSE ONE]} explains what is wrong in the post."

and

"I went to the bank to get money from the ATM, bought fruit at Stop'n'Shop, picked up my sister, and went to the cinema.

Second, the personal pronoun isn't necessary after the first mention because it's the same for all clauses in each sentence, so it can be elided.