I was wondering why my text was reported as having no errors, when I was deliberately putting errors in.

After an hour of trial and error, it turns out that sometimes, the API doesn't like having a period and then a line-feed character in the url-encoded text. LF seems to be encoded as %0A.

Here are the examples that had me isolate the issue:
Text=teh%0Atxet
Reports 2 errors (teh and txet)

Text=teh.%0Atxet
Reports 0 errors.

I don't really need the %0A in my strings so I can just strip them out. Maybe other URLENCODING libraries handle the LF character differently.

But all in all - I'm new with the Bing APIs and I haven't done a ton of web/SAAS programming lately, but this feels like a bug.