Can Lt check for spelling errors when authoring content?

Since Lt is Browser-based, any in-built spellcheck tools your Browser has enabled will apply to any text fields you author:
servlet.ImageServer?id=015w0000002llhT&oid=00D20000000HncM

Lt text panel with Firefox spellcheck enabled
servlet.ImageServer?id=015w0000002llhd&oid=00D20000000HncM
Lt text panel without Firefox spellcheck enabled