Got this feedback from a user today.
The reasoning is that this makes it easy to tell which tasks are completed while on Google Calendar.
She originally suggested adding a “✓” symbol before the title of the Google Calendar event but I thought [X] might be better. It’s semi-standard for Markdown checklists and separates the text and the “checkbox” better.
Would love to hear your thought on whether this would useful and what indicator should be added instead of [X] or “✓”.
Like to see 
️symbol which is logically for me
I like a tick symbol better, but that is just my personal preference. Still, this sounds a bit like a hack to me, and some calendars may not display such symbols properly.
Some other ideas if an item is marked as complete:
For the second option a user can have a separate “completed” calendar which they can either hide, or display in a different colour. The best of both worlds?
While I like the check better, I would prefer the [X] solution. Simply because, while unicode is certainly gaining its place and popularity throughout the world, there will always be situations where the default character set is not fully unicode compliant. This results of course in the ugly square boxes instead ▯ or maybe �
Using a simple ascii character set helps to avoid that.
☒ The check box with an X inside feels more like it belongs in a form field. It could also be a multiple choice box option where you might select several.
The check mark is the universal icon for complete in my opinion.
What @butlermatt said. I love icons but you can’t be sure this will be visible everywhere. So either [x] or [v]
I just started using google calendar sync for my task manager for due dates and was looking for this feature. My preference is to have the items deleted, but that should likely be an option in the settings since that maybe unexpected. I’d be happy with an [X] in the title though if that is easier to implement.
Just started using Dynalist - would really appreciate it if there was something (really, anything at all) available for distinguishing checked items from unchecked items on Google Calendar. Bumping this because I think this (putting a [x] in the title) is the most reasonable option that should be fairly simple to implement.