A language like FORTRAN is also problematic if you need to write a parser/compiler for it.

The well-known assignment mentioned above (DO10I=1.10) is as awful as something like IF(1.EQ.J) - as you have to look ahead in your input stream. Continuation cards make things even worse - so do lesser-known facts ( every character but space and 0 are continuation characters). Besides, being able to write CO N T IN UE instead of CONTINUE is not something you'd ever need - nor is it helpful to spread "STOP" on four lines using continuation characters.

With Fortran 77, first compilers appeared which were less strict when it came to formatting (based on punched cards) and even allowed multiple statements on one line separated by a semicolon. (Besides, the use of INTEGER or LOGICAL arrays for character handling fell out of fashion with the introduction of CHARACTER).