Unless you're German (like me), indentation is a total must, even for two-liners - according to German typography authority Jan Tschichold:
"The beginnings of paragraphs must be indented. Paragraphs without
indent (unfortunately the rule in Germany, and only there) are a bad
habit and should be eliminated. The indention – usually one em – is
the only sure way to indicate a paragraph. The eye, on reaching the
end of a line, is too inert to recognize a tight exit – and in works
without indents, even that frequently has to be produced as an
afterthought from a flush ‘last’ line. In order of importance,
legibility and clarity have to come first; a smooth contour of the
typeset page is of lesser importance. Therefore, typesetting without
indentions is to be dismissed as an error."
Source: Tschichold, Jan (1997): The Form of the Book: Essays on the Morality of Good Design, p.17.