After editing a page and adding a [todo ], reloading the page creates a second time the task, while the task created first still exists in the database (while being associated to no page).

I tried this and it indeed seems to be happening.

Just to clarify for myself, the sequence of operations that triggers this is:

• Edit a page, insert [todo Foo], click save
• Click browser's reload button

My browser (Firefox) gives a warning about re-sending the same POST data in this case. Pressing OK to continue indeed creates a dangling todo that doesn't get its DB references properly updated.

If you click on any other way to reload the page (i.e., copy&paste the current page's URL into the address bar and hit enter), this doesn't seem to happen. It only happens when reload button is used to re-POST.

Yes, it is only when re-sending POST data (I also use Firefox, and I did that by mistake ...). The matter is only to detect users sending two times the same edit ...