Ok, I will call at least a foul here.
Specifically on your (mis) quote of the rule which cuts short the **actual** quote, gives bogus punctuation and isolates it from its context which alters its meaning.
Your (mis)quote was this:
"In many cases, an improvised weapon is similar to an actual weapon."
Putting that as a period ended single sentence makes it look like what you ascribe, but if taken as it actually is its meaning is clear in context.
The statement is talking about how to assign values of damage and damage type etc to the improvised weapon and tie-in proficiencies. Here is the exact quote - unedited.
"Often, an improvised weapon is similar to an actual weapon and can be treated as such. For example, a table leg is akin to a club. At the DM's option, a character proficient with a weapon can use a similar object as if it were that weapon and use his or her proficiency bonus."
The paragraph that follows covers the other case, which helps show you the context again, and shows that even that case can apply to weapons themselves.
"An object that bears no resemblance to a weapon deals 1d4 damage (the DM assigns a damage type appropriate to the object). If a character uses a ranged weapon to make a melee attack, or throws a melee weapon that does not have the thrown property, it also deals 1d4 damage. An improvised thrown weapon has a normal range of 20 feet and a long range of 60 feet."
So, sure, you can edit a cute to cut it short and hide its context to build your rulings on, thats your call. But to me that effort just spotlights the degree of confidence you seem to have in that decision.
But hey, its GM call.
Sure I quoted the relevant part instead of the whole thing, and doing that
could be a 'foul',
if the entire quote would show that it would lead to the opposite conclusion.
But here, the whole rule has the same implications as the part I quoted; that '
improvised weapons' are
not 'weapons'.
"Things that are true, are true."
"Things that are not true, are not true."
"Things cannot be both true and not true at the same time."
Objects are what they are. Even if you
use an object
as if it were a different object, it doesn't change what the object actually
is.
"
Dueling. When you are wielding a melee weapon in one hand and no other
weapons, you gain a +2 bonus to damage rolls with that weapon."
Now, the original version said, "...no other weapon
or shield...". I hated that they took the 'or shield' away. For me, I liked that there were styles for the four basic combat styles: single weapon, two-handed weapon, two weapons, and weapon + shield. This change, allowing the style intended for 'single weapon' to be used when using a shield, especially when shield-users got their own Fighting Style thing, takes away that 'single weapon' niche.
So I houserule the 'or shield' back into the Dueling style in games I DM.
But, if 'improvised weapons'
were 'weapons', then I wouldn't need a houserule! Literally
anything in my off hand would
be a 'weapon', and would prevent Dueling style!
Got a shield? No +2 damage for you, because shields are weapons now!
Wearing a glove? Wearing a ring? Tough, no +2 damage for you, because they
are 'weapons' now!
An object is what it is, and isn't what it isn't. It cannot be both at the same time.
A shield either
is a 'weapon', or it isn't. Which is it?
If we were playing 3e, the answer is definitely 'yes'. Shields are on the Weapons table, as light or medium melee weapons, and can be used in TWF.
But in 5e, shields are
not 'weapons'. They are not on the Weapons table, do not prevent you getting +2 damage from the Dueling style (unfortunately!)
on the grounds that they are not 'weapons'!, and although you can hit someone with a shield via the Improvised Weapons rules (which allow objects that are
not 'weapons' to be used to make an attack), they therefore cannot be used in TWF because TWF specifies 'weapons'.
As an aside (despite seeing the results of my last aside!), shields are not armour either.