Scenery setup:
Place two commandblocks with two button, so you can activate them.
Place in the first the command (say @p, hello.) Don't forget the comma after @p, it is important.
Place in the second the command (say Hello, @p.) Don't forget the point, it is important.
What I expected to happen was...:
The first commandblock give the output (reptle311, hello.).
The second commandblock give the output (Hello, reptile311.)
What actually happened was...:
The first output (@p, hello.)
The second output (Hello, @p.)
When you remove the punctuation mark after @p, it works well. The error too happens, if you use @p[...].
Linked issues
Comments

Sorry, I have used the search function. Must have spelled something wrong. Nothing showed up.

Relinking to MC-10880
Duplicate of MC-9895, please use the search function to see if your bug has already been submitted. Currently over 54% of tickets are being closed as duplicate.