> Basically, no. I did some Googling and came up with the link below, which says, "Do not use extra prepositions when the meaning is clear without them,"

I also did some searching and found basically the same thing. I was afraid the site simply reflected what has become common usage, but its lack of allowing "they/their" to function as a singular so as not to offend people by using "he/his" reassured me. And I certainly agree that language should be as clear and concise as possible.

However, the site I looked at also mentioned verbs that become connected to a preposition to make, in effect, a new verb. to "make out" for example. I would argue that to "jump off" can be its own verb, requiring the use of a preposition afterwards.

Think of it this way:

"I jumped on the bed." One preposition- on. Implies that I was already on the bed, jumped, and remained on the bed.

"I jumped onto the bed." One preposition, but with a compound meaning: I was not on the bed, jumped, and landed on the bed.

"I jumped off of the bed." Two prepositions, implying that I was on the bed, jumped, and landed not on the bed. I cannot come up with a more concise way to convey this, because...

"I jumped off the bed." Being nitpicky, of course, but it follows that this implies that I was not on the bed, jumped, and remained not on the bed.

I realize, of course, that no one actually uses that last example to mean what I said it implies. But it does seem to me a convincing argument for using the extra preposition to ensure clarity.