SC2086 sits at info, ShellCheck's lowest default severity, and fires on every unquoted $var, so it is usually the first rule anyone disables. I built the smallest test I could: a directory holding quarterly, report.txt and quarterly report.txt, and a four-line script under set -euo pipefail:
report="quarterly report.txt"
rm $report
It deleted quarterly. It deleted report.txt. It left the one file it was asked to remove, and exited 0. rm was handed two names and both existed, so strict mode had nothing to catch.
Bash expands the unquoted variable, splits the result on whitespace, globs any * or ? against the current directory, and only then builds the argument list. rm "$report" is one argument with no globbing, and it deletes the right file.
The same bug hides in other shapes. [ $name = "root" ] with an empty $name gives test two arguments: a complaint on stderr, a false condition, and the script keeps walking. for f in $files is not flagged by ShellCheck 0.11.0 at all, and still breaks on the first name with a space.
When you do want the split, such as a flag string read from a config, use an array or a one-line # shellcheck disable=SC2086 with the reason. A repo-wide .shellcheckrc disable covers every future rm as well. And shellcheck --include=SC2086 runs it alone as a CI gate.
Every run, pasted from ShellCheck 0.11.0, is in the SC2086 deep dive on word splitting and globbing.