Among words for "commonplace observations", commonplace itself (or its plural, commonplaces) can be used as a noun with that meaning. Wiktionary defines noun commonplace as "A platitude or cliché" or "Something that is ordinary". Synonyms for adjective commonplace include hackneyed, which is related to words like banal, bromidic, clichéd, shopworn, stock, threadbare, timeworn, tired, trite, unoriginal, and well-worn, which may suggest nouns like banalities, bromides, clichés.
A banality is something "common in a boring way, to the point of being predictable; containing nothing new or fresh." A bromide is "A dose of bromide taken as a sedative", or "A dull person with conventional thoughts [eg] My adviser at college was a bromide who had not had an original thought in years", or "A platitude." Earlier suggestions related to these terms include adjectives mundane ("ordinary; not new" or "tedious; repetitive and boring") and quotidian ("Having the characteristics of something which can be seen, experienced etc. every day or very commonly; commonplace, ordinary; trivial, mundane"). While quotidian is much more frequently seen as an adjective than as a noun, as a noun it means "(usually with definite article) Commonplace or mundane things regarded as a class". One might say: "The Facebook postings in question concentrate horribly on the quotidian and are vapid, mundane, commonplace banalities."