In citations words of one or two characters are not used as keys for lookup. Some users construct special keywords from the volume and page numbers of journal articles, e.g. v74p87. Then they include this special keyword in the citation. Since it is very unlikely that more than one journal article will have the same volume and page number combination, the special keyword is highly effective in selecting the intended journal article. To have flags placed before punctuation use the -P option.
Punctuation is defined as any of the characters .
If it has not encountered any text, then it does not attempt to place flags. The -a option is used to reverse author names. Spaces after author names interfere with author name reversal. The assumption is that titles will be distinct in 20 characters. Let the content of that field establish the proper order.