What is "coder"?

What's "count" mean here? It's different from what it means in "counting numbers", right?

In this context, "count" means "matters." Thus, the speaker is saying "it's the thought that matters [is important]." Ex: Your vote still counts even if you cast an empty ballot. Ex: This is your last shot. Make it count!

Can I use "Get proofed" commonly?

"Get proofed" in this context is a shortened version of "get proof-read", which means to have someone read over something a document that was written by someone else and check for errors. "Proofed" is not a common word to say and it is not actually grammatically correct. The best way to say this is "proof-read". Ex: She is proof-reading my essay so I can edit it.

What does "quirks" mean? Is it a common word?

"Quirks" are interesting or unique behaviors or habits that usually make someone stand out or noticed. A quirk is usually a habit or behavior that other people find weird or interesting. Ex: She has some strange quirks. Ex: He has this quirk where he touches his ear before he eats his food.

Is "on" the only preposition that I could use when I talk about social network service?

When referring to having a presence on social media networks, "on" is the most commonly used preposition. Outside of prepositions, "have" is also commonly used. Ex: I haven't been on Facebook for a long time, so I don't know what people are up to. Ex: Do you have Instagram? Let's follow each other.

He's talking in imperative tone but why "will" was used here?

Yes, he is talking in an official tone! The word "will" was used here to indicate something that is going to happen in the future. It is used both as an instruction and a prediction. In this case, he is stating that everyone in the room will rise when the judge comes in. Ex: Oh, sorry. I forgot your drink. Sally will go back and get it! Ex: Keep watching! You will see how the ballet dancers point their toes.