At http://englishplus.com/grammar/00000135.htm is found the following:
Apostrophes with Italicized or Underlined Items:
Letters, numbers, symbols, and words used as themselves are italicized
or underlined. ...
When these items are made plural, the plural is shown by adding
apostrophe s to the underlined or italicized item. The apostrophe and
s are not italicized or underlined. ...
I find the thee's and thou's in older writing hard to follow. (Words
Lynne Truss also cites this usage in Eats, Shoots and Leaves.
(Unlike the first source above, Truss mentions the fact that there a few pure plurals allowed by some authorities to include apostrophes.)
Notice that these are talking about general, not Facebook-specific, English usages.
PS: My choice of like in the other thread is probably best regarded as arbitrary. Here is a parallel example: 'There are too many hamburger's in your essay.'