Rolf's comment is a fine example of the aphorism 'praise should be delivered in public, criticism in private'. When I spot someone making a grammar error or formatting error or other minor error, I try to PM them rather than make a public comment. For two reasons:

1. People really don't care, and a minor correction shouldn't permanently clutter up comment threads. People reading Benito's request for help don't care whether people dislike the French. Yes, Rolf is right that it's a little annoying and offputting. But if people don't want to read his gratuitous use of French, they especially don't want to read 5 or 15 comments debating it. So criticizing him with a public comment is wasteful of other peoples' time.
2. Criticizing like that in public is especially likely to make someone slightly angry or to lash back or ignore it. So criticizing him with a public comment is less likely to accomplish the claimed goal of improving his writing.