@leahlithe green and red changes with Accept and Reject are consistent with Genie Code’s inline edit or Quick Fix interface. Standard autocomplete produces the grey suggestions you saw before and accepts them with Tab or Enter.

Open your profile menu and go to Settings -> Developer. Keep Autocomplete as you type enabled if you still want the grey suggestions. If your workspace shows a setting for automatic inline Quick Fix, disable that setting.

Databricks treats autocomplete, inline suggestions, and automatic Quick Fix as separate prefeerences. Disabling standard autocomplete may therefore have no effect on the red and green proposals.

P.s. a rejected suggestion should close, and honeslty I could not find a documented feature that recreates deleted cells. Test the behavior in a new SQL notebook. If it continues, ask your workspace administrator whether a Genie code or editor preference changed. Since your colleagues began seeing it during the same week, this may be a shared workspace change or smth.