Some suggestions, mostly quality of life, obvious things

[mbncd]

Isn't that already an option?

Not to my knowledge. If someone's crafting beside you for instance, you'll see the flying icons (and possibly text, I don't remember) of every skill effect they use.

I hope my forum avatar background color can be changed.

There used to (as in in the 1.0 days) be a Lodestone feature that allowed you to pick your avatar, including versions for events you'd participated in and the like. I don't know if this is still possible or not but it might be worth checking.

I would like to disable other players fishing sound

In the bottom of the audio system settings, you can mute all other players. I expect this applies to their fishing rods as well.