When I got the same 403 error while editing this post few days ago, I deleted some URLs first, edited the post, clicked "Save" button, readded the URLs I'd once deleted, and finally clicked "Save" button with composure.
Apparently, we can't edit a post containing more than 4 URLs in it whether the links are embedded or not.
We seem not to be able to post/preview any posts containing more than 4 embedded URLs in any manner. Try a normal link as belowﾂ?ｫ instead of the embedded one [ url=http://www.google.com/~~]ﾆ誰ﾆ椎陳ーﾆ停?愬ｽﾃ板（窶堋ｭ窶堙ｪﾂー窶堙ｱ窶堋ｵ窶堙｡ﾂ） -- crane[/ url].;-)
Oh, then, how about changing all the links into non-embedded version?
I just checked several patterns in this post. It seems that we can edit a post that contains less than three embedded links + less than three non-embedded links, as below.(In other words, this post is the maximum pattern of editable posts.)
When adding one more embedded link, the 403 Forbidden error returns. We can add non-embedded links, but can't edit it. If we want to edit it, we have to delete non-embedded links until the total amount of non-embedded links becomes less than three.
So, I don't know why "3 embedded + 1 non-embedded" can't work in Glenn-san's post.:?
Glenn, I just want to let you know that we have not forgotten about this and the other glitches yet! Currently experimenting with vBulletin 4, I am pretty positive that we shall be upgrading soon and hope that this will solve a lot of the technical issues plaguing this forum.
What does worry me though is porting over the Japanese language section. I hope we won't be drowning in a sea of mojibake...
Thanks for the update, thomas! Yeah, past conversions sure have made things strange in the Japanese forums for some reason. I hope that doesn't happen this time too.