My 9200T formatted its HD worryingly quickly. Instantly done. Is that a bad sign? Is it normally instant? Is there a hidden way to get it to do a more thorough format?

No. If it takes more than a few seconds start worrying.
Yes. It normally takes a couple of seconds.
No.

The reformat rebuilds the index. The 9200T then uses the HDD as required when you record regardless of what was on the HDD before the reformat.

It's roughly equivalent to a Windows Quick Format.

If you suspect the disc has deeper problems which you were hoping a 'full format' would fix then you will have to take the disc out and hook it up to a computer where you can run various diagnostics and fix tools.

Many thanks, Luis and Catbed, for your replies.

Its just a quick format.