I’m not sure how to handle this message. I want to save the changes I’ve made to an .ai file. This is the message I get
Saving to a legacy format may cause some changes to your text layout
and disable some editing features when the document is read back in.
Do you want to continue?
Illustrator honors file versioning. So, if you create a file in Illustrator CS6 and then open that same file in Illustrator CC and you Save. Illustrator will save the file in CS6 format to honor the version the file was created in.
This is similar to how you can create an .imdl file to avoid compatibility issues.
If you don’t want to see the dialog you can do either of two things…
Check the box for “Don’t show again”
Do a “Save As..” and save it as a CC file.