First off, thank you for the valid criticism. Indeed, upon closer observation, the arguments regarding directors, budgets, etc. make the use of actor analogy hopeless. It must be forgotten. (I also wanted to clarify that for me actor appearance is no different from CGI. I mean, some monsters are purely CGI these days: they still appear in stories. But this is still about TV stories, not comics.)
Since we both agree that any frame of a comic is something new (unless copied from another comic), we need to categorise these new things into appearances and non-appearances without resorting to TV analogies. So let me reformulate the classification I proposed in purely comical terms. Needless to say, this all should only be applied to flashbacks, memories and the like:
- Any frame that provides new plot-relevant information about a character is an appearance of that character. (For instance, interaction with characters of the story proper is always plot-relevant and new. But standing in the shade of a tree is generally not plot-relevant, even if not clear from the story of the flashback.)
- Regarding the frames intended to recall scenes from earlier stories, the original TV-based discussion required an appearance to be "re-contextualised to be more than a simple memory of the past". This can be applied to the comic case too.
But before trying to refine the formulation, perhaps, it makes sense to agree on specific appearances. In other words, do you disagree with some of my four examples? Could you provide a specific comic story about the Eleventh Doctor for me to look at: the earlier the better (I haven't read any of them but have the first ones)? And do the flashbacks in The World Shapers re-contextualise the events from the TV stories (I don't have this story and have no hope of getting it)?