I ran into the same problem and found the following to be a good enough solution. Try including this snippet in your olivetti-mode configuration:
(setq olivetti-style 'fancy olivetti-margin-width 3) (defun custom-olivetti-mode-on-hook () (setq-local flycheck-indication-mode 'left-margin)) (defun custom-olivetti-mode-off-hook () (kill-local-variable 'flycheck-indication-mode)) (add-hook 'olivetti-mode-on-hook 'custom-olivetti-mode-on-hook) (add-hook 'olivetti-mode-off-hook 'custom-olivetti-mode-off-hook) This solves the problem for Flycheck indicators, which are likely the only ones you will see with olivetti-mode active.
The bottom buffer below shows the result after enabling olivetti-mode (using the above configuration): 