The above matches:
RewriteRule ^t([0-9]+)-([A-Za-z0-9\-]+)((p([0-9]+))?)\.html$ showthread.php?t=$1&page=$5&pp=10 [L]
But although it is matching t7-testing-p2.html it isn't passing the right parameter to the page= part. I know it's matching because the right page loads but the pagenumber is incorrect. I've tried with $2 all the way up to $7 and it's still not working.
One of those headbanging moments I think
Ah is the p2 part being matched from the previous rule? I didn't want to have to split this into two rules