The description of the paladin's Divine Sense feature says, in part:
You can use this feature a number of times equal to 1 + your Charisma modifier. When you finish a long rest, you regain all expended uses.
Unlike many abilities in 5e, it doesn't specify "a minimum of 1". This brought up an interesting question at my table:
What happen if the paladin has a negative Charisma modifier?
With an 8, you could do the calculation 1 – 1 and get 0 uses, which could make sense, but in our group the paladin rolled a 6 for their Charisma score, so 1 – 2 = -1 uses.
(Please don't comment on our paladin having Charisma as his dump stat; his choice, not mine.)
Best Answer
Technically, negative modifiers apply unless otherwise stated.
You’ve made the right observations: when a negative modifier does not apply, feature descriptions take care to set minimums to avoid things like this. As written, the paladin would have zero available uses of Divine Sense.
Ask the Paladin what they want to do here.
A paladin with 8 charisma is likely not an accident. Choices were made. Ask the paladin how they want to rule on this. Does having zero uses of this feature fit into the character concept they are going for? You’re obviously not going to unbalance things by letting them have one use when they would otherwise have zero (since most paladins have several). So just let the paladin choose which ruling would be the most fun for them.