Generally, in all Japanese language classes, the rule you're taught is that です does not follow い adjectives. Instead, い adjectives can act like stative verbs, and as such terminate a sentence by themselves. However, I have heard this usage frequently. I don't necessarily have a specific example in mind that I've heard, because it doesn't seem all that rare.
However, recently I got into a discussion with someone who suggested that い adjective + です is dangerous, and has the potential to be offensive and/or rude when used incorrectly so foreigners should avoid it. One specific example given was
美しいです sounding vulgar. They also said that い adjective + だ is flat out ungrammatical in all situations. When I've posed this same question to other Japanese speakers, they take no issue with 美しいです and they say it sounds fine.
My question is, there seems to be some disagreement. Does anyone have a definitive answer about why such a disagreement might exist, and how I should go about knowing whether or not it's safe to use い adjective + です in normal usage? Or maybe people here also have no issue with it, and think that the original person I spoke to was perhaps mistaken.
If it's not safe, then what do I do if I want to end a sentence with an い adjective politely? Follow it with ～のです perhaps?