Message to insert tag into HTML filter

I don't think this is really a job for Insert module. Insert doesn't have any concept of input/text formats and it doesn't know which tags are allowed on which fields. It only inserts tags into textareas. Considering the customizations available (like Better Formats) which may hide the tag help from the HTML (plus theming that might do the same thing), I don't think Insert has a reliable source of this information (which means we'd need to add one). It's a lot of overhead for something that's only tangentially related.

Actually I was thinking more about this with a colleague. In reality, no module is going to claim responsibility for identifying this problem, since it's a hard problem to identify 100% of the time. However users of Insert commonly make this mistake, and we could probably solve the problem for 90% fairly easily. If the check fails because filter tips are hidden or there's only one input format, we can just bail on the check and not give an error at all.

So reconsidering I think we can give this a shot, I'll put together a patch and see how difficult this 90% case is.

I've applied this pair of patches which gives the user an error if they insert an image into a text format that doesn't support it. Overall I think this is a good improvement. The error isn't pretty, but it's extremely helpful that the user is at least warned that their image isn't going to work.