include 'win32a.inc'
format coff
extrn '__imp__MessageBoxA@16' as MessageBox:dword
public _demo
_demo:
        push    0
        push    _caption
        push    _message
        push    0
        call    [MessageBox]
        ret
_caption db 'Win32 assembly',0
_message db 'Coffee time!',0    

include'win32a.inc'
format coff
extrn '__imp__MessageBoxA@16' as MessageBox:dword
public _demo
_demo:
        push    0
        push    _caption
        push    _message
        push    0
        call    [MessageBox]
        ret
_caption db 'Win32 assembly',0
_message db 'Coffee time!',0    

$ git diff MSCOFF.ASM MSCOFF1.ASM
diff --git a/MSCOFF.ASM b/MSCOFF1.ASM
index 4eabe64..266daa5 100644
--- a/MSCOFF.ASM
+++ b/MSCOFF1.ASM
@@ -1,4 +1,4 @@
-include 'win32a.inc'
+include'win32a.inc'^M ;<--There's been a mistake.
 format coff
 extrn '__imp__MessageBoxA@16' as MessageBox:dword
 public _demo
    

$ fasmg MSCOFF.ASM
flat assembler  version g.i8q67
3 passes, 201 bytes.

$ fasmg MSCOFF1.ASM
flat assembler  version g.i8q67
MSCOFF1.ASM [1]:
        include'win32a.inc'
Processed: include'win32a.inc'
Error: illegal instruction.
    

    Jule's:    

A single or double quote is not on a list of special characters, neither for fasm nor for fasmg. This means that this character can be a part of a name, like in this example from Understanding fasm 1:

Code:

    Jule's:    

The quotes are only treated specially when they begin a new token. So to have a quoted string recognized you need to have it separated from other name with special characters and/or whitespace. Note how fasm's syntax highlighter that works on this message board emphasizes these rules, including in your samples above.