Good News Translation casts this verse in the plural (“Some people … others…”), which works well in English; other translators may wish to try doing so.

There is one who by keeping silent is found wise: Compare Pro 17.28. It is hard to say here whether the person is thought wise because he keeps silent or although he keeps silent. Perhaps there is a sense of both. If a translator must choose, we suggest “although,” or “even though”; for example, “Some people are thought to be wise even though they don’t talk much.” We could also say “Some people can keep quiet and other people will think of them as wise,” “Some people don’t talk too much, and others think they are wise,” or even “Some people are thought to be wise even though—and maybe because—they don’t talk much.”

While another is detested for being too talkative may be rendered “but if you talk too much, people will not be able to stand you.” The idea is not that the talkative person is actually hated (so New Jerusalem Bible, An American Translation), but that he makes himself unwelcome. People don’t want to be around him. Contemporary English Version has a helpful model with “People who talk too much are not well liked.”

Quoted with permission from Bullard, Roger A. and Hatton, Howard A. A Handbook on Sirach. (UBS Helps for Translators). New York: UBS, 2008. For this and other handbooks for translators see here.