No. All someone would have to do is use the flat side of the sword and they could hit Buggy. But in all seriousness, a Haki covered sword still will not cut Buggy.
Sword attacks with haki can hurt Buggy but can't bleed him as haki can't nullify DF power in which he can't be bleed. Even his body is imbued with haki, Mihawk could still cut him like when Law cut Vergo.
T-Bone was a marine swordsman powerful enough to endanger an entire train. He has sufficient strength to kill Buggy in a single stroke should any of his attacks actually land. However, Buggy has survived against Mihawk, a swordsman much stronger than T-Bone who also knows armament Haki.
On a related note, Mihawk should also be a Haki master. Otherwise, he would've never been able to evenly duel Shanks. Mihawk arguably has the strength and speed to pummel Buggy into the ground. He doesn't need a sword to win this One Piece matchup.
Haki enables physical attacks to connect with Logia users, whose bodies usually prevent the hit. In Buggy's case, even normal attacks do hit him, but the damage is never fatal.
So I thought at that moment Mihawk did not use haki to cut Buggy because before that he meant to attack Luffy who made of rubber, he realized that without using haki Luffy would be torn apart. He also known Buggy and Luffy just an average pirates not yonkou commander level.
He's not particularly strong by any means, but he still holds power in the political atmosphere. However, this is due to a series of misunderstandings by the World Government. Buggy was recently crowned a Yonko by doing absolutely nothing on his part.
Roger used advanced forms of conqueror's haki as he imbued his sword with conqueror's haki and clashed with Whitebeard. He also used advanced armament haki for more powerful sword attacks. Additionally, Roger possessed the observation haki, thus, making him the strongest haki user of all time in One Piece.
Logia, considered to be the strongest class of all Devil Fruits, allows the user to create, manipulate, and become an element or a force of nature itself.
Buggy is easily the weakest emperor of the sea. Without any haki and held hostage by his own crew, his Chop-Chop Fruit is mostly a survival tool. Although excellent against swordsmen like Mihawk and Zoro, he has never effectively used it as a weapon.
He is as strong as he is now. Oda said if he train himself the same as Shanks, he would be as strong as Shanks. Buggy is being lazy. We don't know how strong Buggy becomes after 2 year time skip.
He ate the powerful Bara Bara no Mi devil fruit which allows him to split his body into separate pieces and control those pieces however he wants. Because of the Chop Chop Fruit Buggy is immune to stab and slice wounds, making him a formidable opponent and the perfect character to feature on a One Piece dress shirt.
For weapon users, their weapons become black as well. During a two-year time skip, Zoro trained under Mihawk to become stronger. Part of his training was to learn how to use Haki, and during this training, Mihawk told Zoro that with Haki, any blade can become a black blade like his.
Buggy is not only immune to slashing attacks, he is also immune to piercing attacks.
Mihawk we know from what he says before the strike is trying to cut Whitebeard (flesh or you could argue "vibrations" doesn't matter in either case) and thus didn't intend to cut diamond, and thus didn't cut diamond.
Conqueror's Haki is one of the rarest powers to exist in the One Piece world. Unlike the other two Haki forms, this power isn't accessible by everyone but exists within only a chosen few.
5 Armament Haki Subtype 4: Internal Destruction
The rarest subtype of Armament Haki, known as Internal Destruction, has only been demonstrated by two characters — Monkey D. Luffy and his mentor, Silvers Rayleigh.
Out of all the 7 Warlords that fans have been introduced to so far, Buggy remains the weakest. He isn't particularly good at anything, and his Devil Fruit isn't all that impressive either.
Yes, that's basically what Buggy's doing, except it's the other way around. He's a Yonko because of 'Luck', he runs Cross Guid and has two WARLORDS under his belt by 'Luck'. He has a bigger bounty than Luffy because of 'Luck. ' He has 3.189 billion berries because of 'Luck'.
Kenbunshoku Haki, one of the three Haki types in One Piece, grants the most powerful pirates unfathomable abilities. From sensing people's morality and emotions to being able to predict movements in battle, this form of Haki allows users to tap into a sixth sense that provides impressive precognitive abilities.