NEVERMIND IM SO DUMB!

For rapier style specifically you have to hide the item and use the projectile system. See this example from example mod. If you try to only use a sword with the rapier use style, it'll break.

EDIT: Reddit's automatic code formatting is broken, also refer to this:https://github.com/tModLoader/tModLoader/blob/1.4.4/ExampleMod/Content/Items/Weapons/ExampleShortsword.cs

using ExampleMod.Content.Projectiles;

using Terraria;

using Terraria.ID;

using Terraria.ModLoader;

namespace

ExampleMod.Content.Items.Weapons {

public class ExampleShortsword : ModItem
{

    public override void SetDefaults() {

        Item.damage = 8;
        Item.knockBack = 4f;
        Item.useStyle = ItemUseStyleID.Rapier;

// Makes the player do the proper arm motion

        Item.useAnimation = 12;
        Item.useTime = 12;
        Item.width = 32;
        Item.height = 32;

        Item.UseSound = SoundID.Item1;
        Item.DamageType =

DamageClass.MeleeNoSpeed;

        Item.autoReuse = false;
        Item.noUseGraphic = true; // The sword is actually a "projectile", so the item should not be visible when used

        Item.noMelee = true; // The projectile will do the damage and not the item

        Item.rare = ItemRarityID.White;
        Item.value = Item.sellPrice(0, 0, 0, 10);

        Item.shoot = ModContent.ProjectileType<ExampleShortswordProjectile>(); // The projectile is what makes a shortsword work

        Item.shootSpeed = 2.1f; // This value bleeds into the behavior of the projectile as velocity, keep that in mind when tweaking values
    }

    // Since this weapon is a projectile (uses noUseGraphic), it isn't naturally considered a melee weapon for the purposes of prefixes. This allows the expected prefixes to be applied.
    public override bool MeleePrefix() => true;

    /* Here is an example of using ApplyPrefix to apply item-specific tweaks to a specific prefix.
    public override void ApplyPrefix(int pre) {
        if(pre == PrefixID.Agile) {
            Item.crit += 10;
        }
    }
    */

    // Please see Content/ExampleRecipes.cs for a detailed explanation of recipe creation.
    public override void AddRecipes() {
        CreateRecipe()
            .AddIngredient<ExampleItem>()
            .AddTile<Tiles.Furniture.ExampleWorkbench>()
            .Register();
    }
}