Fortran doesn’t automatically skip comments lines in input files. You can do this easily enough by first reading the line into a string, checking the first character for your comment symbol or search the string for that symbol, then if the line is not a comment, doing an “internal read” of the string to obtain the numeric value.
Something like:
use, intrinsic :: iso_fortran_env
character (len=200) :: line
integer :: dat1, RetCode
read_loop: do
read (1, '(A)', isostat=RetCode) line
if ( RetCode == iostat_end) exit ReadLoop
if ( RetCode /= 0 ) then
... read error
exit read_loop
end if
if ( index (line, "*") /= 0 ) cycle read_loop
read (line, *) dat1
end do read_loop