Send errors on failed comment expansion

[azurelunatic]

Title
Send errors on failed comment expansion

Short, concise description of the idea
When a comment cannot be expanded for any reason, give an error instead of failing silently.

Full description of the idea
Sometimes you're trying to expand a comment thread, and for whatever reason, it does not work. Currently, the page stays the same as it was, and does not give a clue as to what the problem is; the user tends to have to open the thread in a new tab, or refresh the page.

Instead, an informative error message should expand where the comment should have been. Thus the only time there is no action should be when there are problems in communication between site and browser.

Some of the reasons a comment might not expand:
Comment is deleted. (Although this should be pretty apparent.)
Comment has been deleted since the time of page load.
User has deleted themselves and taken their comments with them. (Also sometimes since time of page load.)
User has been suspended. (Also sometimes since time of page load.)
Comment has been screened and you cannot see it.
Entry owner has disabled comments and you cannot see them. (In this case, to avoid giving away too much information that only the entry owner would know, any comment that exists or doesn't exist on a comments-disabled entry should return the sort of error where the only information is that comments have since been disabled.)
Whole entry has been locked since time of page load.
Whole entry has been suspended since time of page load.
Whole entry has been deleted since time of page load.
An ordered list of benefits

• Less user frustration.
• Fewer unnecessary page loads with people refreshing or opening new tabs with a thread for no reason.
• Knowing when it is time to refresh.
• Good programming principles?
• If it's enough of a drama to attract the drama-llamas, they are probably already making their screencaps without other prompting.

An ordered list of problems/issues involved

• Likely slightly more expensive to send an error instead of failing silently.
• Is the tradeoff in good user experience and saved page loads enough to offset the small extra expense in sending errors, and the cost to develop?
• An error message that indicates that something's disappeared will give drama-llamas more of a chance to make screencaps.