I often spell things incorrectly, often as I write so much and get some typos creeping in. I do my best to check everything after submitting and go back and correct things as it is difficult to follow posts where misspellings are apparent, which is why many of my posts show they have been edited.
Purposeful incorrect speling is a nusiance to serious readers and serious readers and posters is what all should we wish to encourage.
Banning a poster is a serious matter - though so too would be repeated ignoring of a Moderators request to follow posting rules.
There is quite a lot of this creeping into the forum and I personally would support the Moderator in what would seem to me to be reasonable request.