The two sentences that use a comma in a way that is considered contested usage are:
-
Stephen did not understand the question, and so Gina tried to explain it to him more clearly.
The comma before "and so" can be seen as contested because it's often debated whether a comma is necessary in such cases, as it depends on whether the writer wishes to emphasize the conjunction or the connection to the previous clause. -
Faith, Millie's best friend from summer camp, is coming to visit in a few weeks.
The commas around "Millie's best friend from summer camp" are also sometimes contested, particularly with whether such a phrase should be considered non-essential information or if the sentence would still hold meaning without it. Some might argue about the necessity of the commas in this context.
These usages highlight instances where different style guides and writers may offer differing opinions on comma placement.