Showing possession of nouns that end in s

[paradoxical]

This is something that has been bothering me for awhile. Somewhere along the line, I came to believe that it was grammatically incorrect to use an apostrophe to show possession of plural nouns ending in s, as well as proper nouns ending in s.

Ex.
The visitors comments (vs The visitors' comments)
The boys bicycles (vs The boys' bicycles)
Jesus son (vs Jesus' son)
Dickens story (vs Dickens' story)

I believe I learned this from The Elements of Style. Both my copies are missing, but I'm pretty sure it specifically said that there are no such words in the English language as boys' bicycles or Jesus' son and I considered it a point of pride not to use these kind of words. However, this "incorrect" usage appears everywhere; and consulting Simon & Schuster's Handbook for Writers, it appears that I am wrong. (I don't remember exactly what I was taught in school, but Handbook for Writers was the text used when I was a Freshman. I believe I learned all of this later using the Elements of Style). I also did a web search and apparently it is considered correct to use the apostrophe in MLA, AP, and Chicago format. What gives? Did something change since the release of Elements of Style? Also, one final question, if that is all right. Do you use an apostrophe for acronyms and initialisms? This is another case where I thought I was right and everyone else was wrong (I never used an apostrophe, just added an s. Now it seems that it is considered proper grammar to use an apostrophe).

Ex.
UFOs vs UFO's
CDs vs CD's
IOUs vs IOU's

[Calidore]

I wish I had my copy of Elements of Style handy to check, but I've never heard of anyone saying that an apostrophe was incorrect in your first case. If it's a possessive or a contraction, use an apostrophe. If it's a plural, don't. If it's a plural possessive ending in "s" (or the original word does), use an apostrophe at the end. This also applies to your second question.

"I've seen a few UFOs."

"The UFO's crew looked just like us."

"The UFOs' collective noise made conversation impossible."

[paradoxical]

I wonder if it's an older form of usage? I believe you are correct, but "The UFOs' collective noise" still doesn't look right to me.

[OrphanPip]

You double the s only with pronouns that end with s, like James's. There are sometimes exceptions made for Biblical names though.

[paradoxical]

Thanks for clearing that up for me. I realize now where the confusion started: I read how the possessive of pronouns such as its never get an apostrophe. That it's was incorrect unless used as a contraction (which I already knew) and that there was no such word in the English language as its'. That's where the trouble started.

The style guide also recommend using the apostrophe-s and not just an apostrophe if the word ended in s. Somehow, I misread all that and came to believe that one should never use just an apostrophe to show singular possession of a word ending in s. Pretty dumb, really. Thank God I was "breaking this rule" most of the time.