Possible insanity, or is it LC 7.0.1?

[Graham Samuel]

Using LC 7.0.1 on Yosemite 1010.1, when I type this into the message box

  put (1.884955 is a number)

I get true, as expected, but if I put

  put (1.884956 is a number)

I get 

Script compile error:
Error description: Expression: unquoted literal

This result was derived from some complex code so I originally thought that the character string could have been corrupt with invisible characters,  but I retyped the numbers myself. This seems so mad that I need someone to confirm it, even though I find it completely repeatable. I tried it on LC 6.7 (which just happens to be on my machine) and I got true as expected.

Someone tell me I am not crazy.

TIA

Graham