Edit: The command I used was wrong, but when an invalid command is used, instead of a syntax error or the command not working, the command block returns "Request to create Minecraft:(particle_name) sent to all players in the output box.

Steps to reproduce:

1) Use an invalid particle

eg- /particle minecraft:flame ~~~

OR use the execute command

eg- /execute (playername) ~~~ particle minecraft:flame ~~~

2) Enter the command.

Observed results:

Instead of executing the command, it says: 

 "Request to create particle sent to all players"

Expected results:

Command block should be blank (in the output section).