[Reader] placeholder for missing pages

[Tristan__]

I was talking with @glad-barfs on Discord about missing chapter pages and he sent me a few examples of groups that have been inactive for years with no way to contact them with chapters that are missing pages.
What if moderators had a way to add a page placeholder to those chapters where the page should've been until someone provides the mods with the missing page of that group.

Pro arguments (positive effects):

• The double-page reader mode doesn't break
• The reader can see if the chapter has missing pages and can warn users before they start reading (when the user opens the chapter), like with the chapter gap warning.
• Users don't get confused by sudden changes after an image is missing.
• Users with enough time can see where images are missing and can go file hunting in some archive.
• Moderators don't get continuous reports about missing images for cases that are already known by the moderation team.

Counter arguments (negative effects):

• Users are expecting images and not some warning.
• Users that would normally not notice and just wonder why the pacing is weird would notice the missing pages (e.g. the same people that report manga with no chapters for having no chapters and asking MD to translate them).
• Mods have to manually add and remove the placeholders.
• More work for developers to implement and maintain this (e.g. reader would have to get changes to render the placeholders between the images. Backend and uploader work too).
• May break 3rd party services. There shouldn't be a change to the chapter images array.

Of course a setting that would disable the placeholders would also be a good idea.

The placeholder can be some static image like agg.jpg, or it can be html that is inserted by the reader.
As an example, here is the reader placeholder for a long strip chapter that was just uploaded where the images haven't finished processing:

Spoiler: Image

 

[OisE]

the same people that report manga with no chapters for having no chapters and asking MD to translate them

 

[BraveDude8]

I could just put a white page in the chapter with "this page is missing, please report this chapter with a link to it if you find it" and that wouldn't require anything new or cause any compatibility issues.

 

[Tristan__]

I could just put a white page in the chapter with "this page is missing, please report this chapter with a link to it if you find it"

Well yes. But that wouldn't allow the reader to know about missing pages and show users a warning popup.
I would feel jebaited if I read a whole chapter and then the last page is just "mod note: last page is missing". I'd rather wait and see if the missing page will be added after a few weeks.
Another way would be just the missing page warning with an optional mod note.