A colleague explained to me that it is a typographical rule to not set an indent for the first line of the very first paragraph of a text, the one that starts right after the headline. Instead, the indentation should start with the second paragraph. However, I am finding examples in various publications where the indentation starts right with the first paragraph. Then again, others do it the way it was told me.
Is there a “right” way to do it, and if so, why? If not, what are the advantages/disadvantages of either method?
First of all, the point of indenting the first line of paragraphs is to help the reader distinguish adjacent paragraphs when reading or skimming the text. Doing this in addition to not justifying the last line of a paragraph has several advantages:
The non-justified line may still take up almost the entire linewidth.
It is helpful to have some sort of orientation at the left side of the paragraph to help your brain find the right line to continue. If you only have a straight wall of text on the left side of the paragraph, it is more difficult to find the correct line.
Not justifying the last line of a paragraph does not work with unjustified text. While the last line is still shorter on average, there will be cases which are impossible to identify as a last line of a paragraph.
Obviously, this advantage does not apply to the first paragraph. Here you have the following dilemma:
Indenting the first paragraph causes some optical dissonance because the gaps in the left side of a text block are unbalanced: You start with a gap, but you do not end with one (unless you have an orphan which is bad for another reason). Also the point where you have to start reading is somewhat more difficult to find: For example, if you follow the left edge of the paragraph to the top, you will end up at the second, not the first line.
Not indenting the first paragraph makes paragraph formatting somewhat inconsistent.
In my opinion, the first problem is more severe, but that’s, well, just my opinion.