I explained that in the post I gave some moments ago:

http://www.flyertalk.com/forum/19029066-post155.html

See the third or fourth paragraph and also further down where i highlight the differences between someone making commericial posts and someone with a commericial sig making posts that add value.

Now I've answered your question, can you answer mine?

What is the benefit of banning commercial sigs?

I've never asked a question of a TB, some of which members seem SOOO determined to act, but who cannot actually identify a benefit for the course of action they seem determined to pursue. This is just not logical that some members seem determined on a course for something they cannot actually describe a benefit for Surely it's not much to ask that you can describe the benefit to us, the members you represent, before you actually make a change which negatively impacts on members using commericial links and on the mods you expect to enforce the change you make.