Thunderbird inserting extra blank lines

[slickrcbd]

Lately Thunderbird has started inserted unwanted extra lines.
I've been doing a weekly thing where I recommend an old fanfic from the HP series to the Yahoo groups harry_potter_recs_n_links & CaerAzkaban.
I tried to copy/paste the information from Fanfiction.net on the story, and haven't had an issue until today. Now it keeps inserting unwanted line breaks. Also the font and size seem slightly different from the message body AND from what it appears as in the Word document where I have my notes. How do I get rid of the extra spacing?

https://www.flickr.com/photos/10736018@ ... 4159585762

I have been having similar issues with trimming quoted text. I'm a bit old-school, having learned posting protocol from Usenet back in the mid 1990's and was told that e-mail was almost the exact same, back when some people had mailboxes as small as 300 kilobytes (NIU did this even as late as 2001 for student e-mail accounts.)
Trying to cut off unnecessary stuff and insert a ==snip== tends to insert extra line breaks where the ==snip= is and gives you whitespace between the ">"'s.
> some quoted text ==snip==


> Some more quoted text

When I would prefer
> some quoted text ==snip==
> some more quoted text


How do I fix it?
Due to the group being before Neo and set to strip attachments, I've been setting it to compose in plain text, (although recent evidence in the last 6 months indicates that HTML e-mails are now working properly instead of being screwed up by the attachment stripping program as it did for ten years.)
It is a Yahoo group, and I am NOT a moderator, don't focus on that, just accept that I'm composing in plain text.