no significant changes…

but you want to customize meta descriptions on per topic basis??

I think a better approach would be to change this option from:

Use custom description on main forum page only and use forum description on forum pages and use topic title on topic pages

to:

Use custom description on main forum page only and use forum description on forum pages and use 141 character excerpt on topic pages

There is no point to repeat the topic title in the meta description.

i agree with the ghostbuster! :).

That is wrong.