Sure! I'll go through each sentence and provide feedback on its correctness. I appreciate about your comment. Correction: I appreciate your comment. Explanation: The verb "appreciate" does not require the preposition "about." Simply saying "I appreciate your comment" is grammatically correct. I appreciate that you sent the email to me. Correct. Explanation: This sentence is grammatically correct. You are using "appreciate" correctly, followed by a clause that expresses what you appreciate (i.e., "that you sent the email to me"). I would appreciate if you send the email to me. Correction: I would appreciate it if you sent the email to me. Explanation: In this sentence, you should use "it" before "if" to introduce the subordinate clause. Additionally, it is more appropriate to use the past tense "sent" after "if" to maintain consistency. I would be appreciated if you send the email to me. Correction: I would appreciate it if you sent the email to me. Explanation: Similar to the previous sentence, you should use "it" before "if" to introduce the subordinate clause. Additionally, use the past tense "sent" after "if" to maintain consistency. It would be appreciated if you send the email to me. Correction: It would be appreciated if you sent the email to me. Explanation: Again, similar to the previous sentences, you should use the past tense "sent" after "if" to maintain consistency. That is appreciated. Correct. Explanation: This sentence is grammatically correct. It simply states that something is appreciated. That is appreciating. Correction: That is appreciated. Explanation: The verb "appreciate" does not typically take the present participle form (-ing) in this context. Using the simple past tense "appreciated" is more appropriate. I hope this clarifies the grammar usage of "appreciate" for you. Let me know if you have any further questions!

Just to add a note to Ahmadi's excellent explanation. Appreciating is often used to mean growing in financial contexts. The share price is appreciating steadily. - It's growing steadily. The opposite is depreciating.