Actually, the original questioner was wrong all through. “Acting strange” and “acting strangely” are both entirely acceptable. Vide the OED, s.v. “act”.
Yeah, I remember noticing that the last time that one came around. Both work, because “acting” can be both a linking verb or an action verb. “He is acting in a strange manner” does not sound incorrect, does it? Well, “in a strange manner” is an adverbial phrase that means the same thing as “strangely.”
This reminds me of a bit by comedian George Wallace. He says when he was young, his mother made him go to his room and told him “Don’t come down until you learn how to act.” So then, he says, he was up in his room saying “To be, or not to be…”
I agree, “acting strangely” and “acting in a strange manner” mean the same thing, and both of them make sense. But it seems like a slippery slope from here to admitting that “I felt badly” is okay, and then god help us all.
“I feel badly” is okay, but has a different meaning than “I feel bad”. Someone who feels badly might be numb, or have nervous damage, or otherwise have an impaired sense of touch.
Or you can feel bad about prepositionating a sentence endifing of.
“Slippery slope” is always a slippery slope; in matters of natural-language idiom, it’s a straight downhill schuss into madness.
Fortunately, “felt” does not have a active verb form that means almost the same thing as its linking verb form. “Acting” does.
I actually would not say that someone is “acting bad,” as “bad” in that form connotates evil. I would use “acting badly” whether I meant they were behaving in an unpleasant manner or doing a poor job on stage.
When you’re up on stage playing the part of Snidely Whiplash, you are acting bad. When you are supposed to be playing Snidely Whiplash and you come across sounding more like Dudley Doright, you are acting badly.
And as some wag remarked years ago, the only person with a right to say, “I feel badly,” is an inept dirty old man. But “act” means more than one thing, and in the non-theatrical sense, it happens that “act strange” and “act strangely”, when applied to the real world, end up meaning more or less the same thing.
Language is a lot more complex than our schoolteachers wanted it to be.
‘…ending in “of”’ would be OK, wouldn’t it?
Anyway, condemnation of the prepositional sentence ending originated in a pedantic 19th century grammar text whose pedantic author thought, with no linguistic justice at all, that English should conform to Latin grammatical practice. Somehow the fool idea caught on, even though it was never recognized by the likes of Shakespeare and Milton.
Hopefully another master of the the English language will eventually have the last word:
“This is the type of nonsense up with which I will not put” (Churchill).
I can never remember whether it was the “rule” against ending a sentence with a preposition or the “rule” against splitting an infinitive that C. S. Lewis called “a Frenchified schoolroom superstition”, but it applies to both.
Person 1: Who are you going with?
Person 2: That’s bad grammar, you’re not suppose to end a sentence with a preposition.
Person 1: Okay, Who are you going with, Stupid?
Here’s another version:
African-American Harvard freshman, 1st day on campus, asks random passerby who happens to be a Preppy Harvard senior:
“Hey man, where’s the library at”?
Preppy Harvard senior: At Hahvahd university we do not end our sentences with prepostions!
A-A freshman: A-w-w-rat then, wuh’s duh liberry at, you muthafucka?
Well, “Where’s it at?” is wrong, not because it ends with a proposition, but because it ends with a pointless proposition. As a Buddhist might say, where already has at-nature.
You mean preposition. I hate to think what might happened if the senior preppy had suggested that the A-A frosh was propositioning him.
Whoops! Yes, I meant “preposition” of course. Nowadays I talk a great deal more about propositions than prepositions, and my silly fingers went the wrong way when I took my eyes off them for a moment.