Immediate Shutdowns

Greetings,

Are there long-term detriments from executing an immediate shutdown and/or
issuing SIGQUITs to either the parent or any child postmaster? I'm aware
that PostgreSQL, upon next start, performs a WAL replay and performs other
crash recovery steps. Are there certain operations, such as VACUUM
ANALYZEs, CREATE INDEXs, INSERTs, UPDATEs, and/or DELETEs, for example,
that are less easily recovered or less recoverable than other operations?

What might cause an operation, such as a VACUUM ANALYZE, not to exit upon
receiving a SIGTERM. Are there any circumstances when a SIGQUIT could fail
to cause an imminent exit (other than a process in an fundamentally
unreceptive state, such as an uninterruptible sleep).

Thank you in advance,

Harold Falkmeyer