As described in HELP-13345, there appear to be several small bugs regarding type validation of field values in the edit/insert document UI. Specific examples:
1. If you have a field of type Int32, and paste in a floating point number (eg. 123.45), it won't complain. (Whereas if you tried to type out 123.45 it would just refuse to add the decimal.)
2. If you have a field of type Double, and set a floating point value (eg. 123.45), you can flip the type to Int32 and it won't complain.

I've confirmed these issues are reproducible in compass.