When a collection field has a character limit, you are alerted to the fact when you type and get close to the limit – but only when you edit the content on in the collection item form.
However, when you edit the same content within the page layout, there is no such alert. On the contrary, the field on the page accepts whatever is input, making the collaborator think that all is ok. The tiny 'Error' label in the editor bar is not sufficient! Firstly, it is easily missed, and secondly it doesn't explain anything.
At the moment, the collaborator either navigates away from content that was too long thinking it's been accepted, or is left wondering what'd wrong.
I think that this is a major flaw that needs improving.