http://www.tmcnet.com/usubmit/2011/01/16/5247199.htm
According to state law, write-in candidates are permitted only as the legitimate substitute
of a candidate who has died, resigned, withdrawn or been removed from the race.
That applies to every race, whether it’s a primary, special or general election at
any level of government, said Pamela Weaver, communications director of the secretary of
state’s office.
But every election ballot includes a space for write-in candidates, whether or not one
is needed for that race. It’s there just in case a write-in does become eligible.
And that’s perhaps where the confusion occurs, since some people see the space and assume
write-ins are allowed in all elections.
end snip
Mississippi Code: 23-15-365
http://law.justia.com/codes/mississippi/2013/title-23/chapter-15/article-13/b/section-23-15-365
They also have filings for independent candidates in Mississippi. It doesn’t say that they all have ballot access. I’m not sure that this law you’ve cited deals with all the possibilities for write-ins in Mississippi.