ADDITIONAL SYSTEM INFORMATION :
Artix Linux
OpenJDK build 20-ea+22-1594
Temurin build 19+36

A DESCRIPTION OF THE PROBLEM :
JShell appears to echo in an awkward manner non-elementary expressions that I pass through stdin. The same thing happens with every feedback mode. "/set format" does not seem to have any effect on this issue.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
jshell <<< '"test".toUpperCase()'
jshell -q <<< '"test".toUpperCase()'
jshell -s <<< '"test".toUpperCase()'
jshell -v <<< '"test".toUpperCase()'

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Something like
    jshell> $1 ==> "TEST"
or—if this echoing is intentional—
    jshell> "test".toUpperCase()
    jshell> $1 ==> "TEST"
(and in that case an option to disable it).
ACTUAL -
    jshell> "test".toUpperCase()$1 ==> "TEST"
and similar outputs based on feedback mode.

FREQUENCY : always