The sentence contains a dangling modifier, the best way to revise it would be:
A dangling modifier implies a word that modifies another such as an adjective is not placed next to the word it modifies or the word has not been included.
A misplaced modifier occurs as the modifier is placed incorrectly, which causes it to modify a different word.
The sentence baffled by the abbreviations, the directions were essentially useless, contains a dangling modifier because we do not know who is baffled and due to this, it seems the object baffled is the directions, which is illogical.
Any sentence with these types of errors can be corrected by adding the word that is modified or placing the modifier correctly. The best way to revise this sentence is:
The directions were essentially useless since the reader was baffled by the abbreviations
Which adds the word modified or the person that was baffled.
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