tl;dr version: Thanks for the feedback everyone! I appreciate it and I've read through every comment so far!

Long version: (sorry if there are several typos in the text. I haven't looked it through properly yet.)

I wanted to thank everyone who has supported this taunt by voting for it on the Steam Worksop and for giving feedback.
The many respectful comments with kind words and honest criticism has made me value what people think. I'm very happy that people are positive about it in general and that I'm able to learn from the opinions.

I wanted to adress some statements and suggestions that have been said in the comments both on Youtube and Steam. Below are some replies to anyone who stated something similar.
But remember. While I did much, I wasn't the only one involved in the making of the taunt, so I can't speak for anyone but myself.

Taunt could be tweaked/polished: Agreed. Due to time constraints, it was decided that its current state was "good enough". There were a total of 9 times that the animation was tweaked over and over. Thankfully it's now looking way better than it could have. If it wasn't too late now, I'd probably look over what could be improved again.

Taunt being able to tauntkill: This was never the intention, because so far the only taunts being able to deal damage are implemented with weapons. However, I'm not against workshop taunts having tauntkills in general, as the 'Hoodoo Hex' taunt on the workshop is a brilliant example of why it could work in my opinion.

Taunt being continuous: While doable in theory, this taunt is intended to be long enough for one voice line to be played. For it to be looping, it could either be silent, or display lines over and over similar to the RPS taunt, though I doubt this idea personally.

Taunt being multiclass: The whole idea of the taunt was inspired by 6 of soldier's voicelines. (hatoverhearttaunt01--06) No other class have lines labled as such. Nor do all classes have lines that fit the "Rest In Peace" setting the taunt is going for. Eventhough the lines are Vavle's choice, it seemed safer to use existing ones.

Stone breaking when it falls: Due to time constraints again, giving the stone model several bones that split was difficult, so it was decided that the grave could just fall in a simple way.

Title of taunt: Somebody in the comments suggested the name 'Maggot's Memorial' which I can see working aswell.

Video's audio being out of sync: Exporting error on my end when getting it from SFM to a video file. I don't intend the sounds to be out of sync if it gets in to the game. My apologies.

Stone impact sound being too loud: I can agree. I simply didn't realize it until it was too late and comments pointed it out. Valve has full control over what audio is used, so hopefully it might be adjusted if it gets in to the game.

Stone falling after the soldier's salute is done: Understandable. This was originally how it was planned to be. However, I felt that there would be a lot of empty animation on the soldier if he were to wait until the gravestone fell. Although this desicion is very subjective, and I'm aware of how much sense the other idea makes, considering it would give the taunt a clearer comedical pacing etc.

Soldier stepping a bit to the side when he salutes: This was overlooked while animating, because I didn't mind that much how he stood. I agree that it was lost potential though.

Text on the grave: When choosing the style of the text, I chose to use 'Expiration Date' as a reference. In that video, when the soldier says to the spy "You did not read mine!", he's holding a piece of paper that reads "Soldier", which I can only assume is his own handwriting. This is the reason why I didn't try to go overboard with the crudeness.
As for what the grave says, there were many ideas in mind, but no absolute winner. Thus the current one happened to be used.

Halloween only: According to TF2's webpage, items like this one can be visible for the whole year if Valve accepts them. Because of this, the taunt is supposed to not be too overboard with sp00ks even if it's made mostly for Halloween.

Then again, none of this will matter unless Valve accepts it in the end. It's up to what they and the community decides. Thanks again for reading.