Right now if I select "Based on Sender (from)" it assumes that I want to have
both a From and To filter in the new filter.  I believe this is a bad
assumption that does not apply to all users.  I appreciate your consideration
for this request.

I can add this as additional global option (which will be disabled as default):

[x] disable two-way address search terms

tooltip: By default, quickFilters fills 'from' and 'to' search conditions to
aid filtering message threads including your own emails to the recipient. The
Addon 'Copy Sent to Current' can be used to keep replies with their original
emails. If you always want to keep your replies in the Sent folder, activate
this option.

I will probably also add a link to:
https://addons.mozilla.org/en-US/thunderbird/addon/copy-sent-to-current/

to make the use of two way filtering more obvious

Created an attachment (id=7796) [details]
2.4.1 prerelease 1

Here is a first stab at the feature. Hope the tooltip is reasonably
understandable.

Created an attachment (id=7797) [details]
2.4.1 prerelease 3

Improved tooltip with more accurate wording and moved Copy Sent to Current to
end.

Reopening bug - at the moment (version 2.6.1) two-way addressing seems to be
permanently disabled.

Fixed - Version 2.7.1 (?) - 27/10/2014