The rules in rules in D&D don't make sense, as situations crop up that the creators of the game couldn't anticipate.
The current edition of D&D is relatively exploit-free. This is due to the fact that the creators of the game can quickly post errata on social medi, in order to officially shut down any loopholes that players start to abuse. This happened with the conjure woodland beings exploit, which allowed players to summon a squad of Pixies that could cast the polymorph spell. All it took was one tweet to shut down the roving band of Pixie campaign breakers. The older editions of D&D weren't as lucky, which led to the creation of lots of house rules to patch the holes the game. Many a DM had to lay down the law in order to stop players from messing with their campaigns.
Each edition of D&D has positive and negatives when it comes to rules, yet there are some that are hard to wrap the head around. These range from being able to survive a fall from any height, to being able to assassinate a big pile of goo.
Weird D&D Rules: The Limitations Of Gravity
In D&D, there are limits to how much damage a character can take while falling. According to a 10th level Barbarian with a good Constitution score could easily survive being thrown from a spaceship, especially if they enter Rage just before hitting the ground, as they would gain resistance to bludgeoning damage. Even hitting the ground isn't a death sentence, as it's possible that a D&D character can their death saves and just be left unconscious.
Weird D&D Rules: Making Money & The Cost Of Goods
This was more of an issue in the older editions of Dungeons & Dragons, but the cost of goods never made much sense. This has led to exploits that allow players to earn infinite amounts of cash, like D&D's ladder loophole, where a price disparity between 10ft ladders and 10ft poles created an endless cycle of cash for the party.
The developers of the game were never trying to accurately replicate a financial system, as trade in D&D only exists for the player's benefit, so it's not surprising that these mistakes weren't known until after the rulebooks were published. D&D doesn't really work as a feudal lord simulator, but fans who are interested in that kind of gameplay should check out Pathfinder: Kingmaker, as it uses similar rules and has a story based around creating a fantasy kingdom.
There is also the cost of goods to consider. In Dungeons & Dragons third edition, there were expensive gimmick items that could be used to aid the party. These included items like Thunderstones, which made a loud noise when thrown against a surface, or a Tanglefoot bag, which contained a sticky substance that could temporarily trap enemies in position. These D&D items were incredibly expensive to purchase, in order to stop players from abusing them, leading to a Tanglefoot Bag costing fifty gold pieces.
These prices are highly inflated, compared to the cost of hiring mercenaries in Dungeons & Dragons. A player could hire an army of 150 soldiers for the same price as one Tanglefoot Bag. Traps were also incredibly expensive, as a camouflaged pit trap (one that is dug with a spade and covered with leaves) cost 1800 gold pieces to make. The player could hire the Rohirrim army from Return of the King for the price of a few pits.
Weird D&D Rules: Jack Of All Trades Turns Bards Into Warriors
One of the perks for Bards in D&D is their 2nd level Jack of All Trades ability. Jack of All Trades allows a Bard to add half their Proficiency bonus (rounded down) to any ability check that doesn't already include the bonus. This technically means that Bards can add their bonus to their Initiative checks, as it meets the criteria listed above. The only other Dungeons & Dragons class with this benefit in the Player's Handbook is the Champion subclass for Fighters, with an ability they don't get until level 7.
This means that a Bard with a high Dexterity score is one of the fastest warriors when it comes to acting in combat, outpacing all of the martial classes (save for one Fighter subclass), Monks, and Rogues. Bards are meant to be primary spellcasters with a ton of special abilities who can be made into competent warriors with subclasses, yet they can be swifter than almost every other class in the book.
Weird D&D Rules: Sneak Attacks For All
The best weapon in the Rogue's arsenal is the Sneak Attack. This allows them to add damage to an attack roll if they have advantage against a foe, or if an enemy of the foe is within five feet of their position. Sneak Attack is one of the greatest combat abilities in the game and many parties will switch their tactics on the fly, in order to let the Rogue deal as much damage as possible.
The Sneak Attack ability is described as taking advantage of a foe's distraction, but what if that foe cannot be distracted? In the third edition of D&D, Sneak Attack only worked on living targets with discernible anatomy, as it didn't make much sense for Rogues to be able to get the drop on an undead skeleton, a robotic golem, or a pile of ooze.
This change was made to make Rogues more effective in battle, as Sneak Attack was very situational in D&D third edition. Rogues took a nosedive in usefulness whenever certain types of enemies showed up, so the new Sneak Attack rules help to keep them in the game, but they don't make much sense in the context of Dungeons & Dragons.
Source: DnD Beyond
