Yeah, I know that's very irritating. Before saying anything else, welcome to the forum, polarboy.
Well, I use Opera exactly because of those "little details".
With that browser, if you type something and then you realize you have to login (or even to register!), you simply do it and then
you use the "Go Back" button. The text you typed is still there, it's very hard to lose any editing.
This "keep-the-text-you-wrote" feature also works in Wikipedia, when you edit an article. Sometimes I edit an article and then I realize I didn't login. I don't like to edit Wikipedia anonymously, or the page could be locked for edition only by registered users. Well, I just login, I go back, and voilá, the text I typed is still there.
It works in any forum. It also works when you post in one of those forums that require you to write a random number or a random text (to exclude spambots). If you forget to write the random text before posting, you can go back and the text you typed is still there.
Same thing happens when you have to fill one of those long forms to register at one site. It's frustrating to write your address, your name and your whatnots to find you made a mistake and that you have to retype everything. Well, you go back and, zing, the things you typed are kept for you.
I don't know if you can do the same with Firefox, Safari, Chrome or IE.
Frankly, I don't understand why people use those browsers. They are always playing catch-up with Opera: I can mention half a dozen "breakthrough" characteristics of Opera that have been copied by IE and Firefox years later. Opera is incredibly lightweight (it's 9 Mb download) and is
fast, as fast as Safari, much faster than IE and slightly faster than Firefox or Chrome.
You wouldn't believe the time you save with that browser, from the ability to read aloud the news while you post, to the fact that you can double click on a word (on a page only) to to translate the word or to get a dictionary definition of it. You have the mail and your contact list embedded in your browser, that's also a time saver.
You can also right-click anywhere on the post while posting, to check the spelling of your post (I wish everybody did that!).
This "keep the text you typed" feature
makes easy to go back to consult a previous post on the thread, even if it's not in the "last page" (you know, the list of previous posts that appear at the bottom while you post, only covers the last page of posts).
Be careful: if you "go back" and then, before "going forward to your text",
you open other page, you lose the ability to "go forward" to the text you typed, but that's logical.
Let's say you go back and then you want to read a previous page of the thread: you simply go back to be able to see the list of pages in the thread.
Then you click with the middle button of your mouse on the page number of the thread to open the page that you want to read. This means you open the page in other tab. You can do that in many browsers, I know, but then, with Opera you read what you have to read and then you go to the tab where you were typing. You simply "move forward" to continue your post. The text is still there.
That is very handy: I have (frequently) to go back, middle-click on the forum main page, search for other thread, copy the link to that thread or the link to an image of that thread, and then I can move back to where I was editing, to insert the link.
Finally, let's say you write a post, you submit it and then you edit it: you can lose part of your post and decide you need it back. Easy: you can go back to your first post, before the edition. The text of all your editions, no matter how many times you submitted them, is still there.
Unfortunately, that kind of abilities makes me to post very loooong posts, filled with pictures and links.
It's not my fault, it's Opera's, guys.
I can feel your pain, polarboy: not only I spend a lot of time posting, but I get nagged frequently for "talking too much" (I'm the kind of guy that actually appreciates 2 hours posts, sorry fil!)... but at least I don't lose what I write.