The problem is simple: searching the forums for any two-keyword query is a write-off.
I'm not talking about two-word phrases, those can be solved by searching with quote-marks - I'm talking about narrowing searches.

Say I want to find posts about people using restraints in bathtubs. ""Bathtub restraints"" is probably going to be far too specific for what I'm looking for (it is, 0 results)
However as far as I can tell searching just "bathtub restraints" with no quote marks brings me all the results for "bathtub" AND all of the results for "restraints", which is woefully unhelpful. God forbid your search contains the word "gunge".

Also, a way to search only top-level posts would be great instead of always including replies.

And if there are options for either of these issues - they're not obvious enough!

You're right, and it's not so obvious that you can ensure a word is included by adding a + sign in front it. So searching +bathtub +restraints is probably what you wanted.

I've just made a change to UMD's forum search that internally implies the + signs automatically. So now all your search terms are guaranteed to be present in the result. Check it out and see how you like it? Thanks for the idea... I should have done that a long time ago! I'll update other searches around UMD soon as well.

As for an option of searching only top-level posts, I'll consider that for an advanced search option in the future.

This worked a treat!

If/when UI changes for search come when you tweak advanced search, it would be very good to add a [?] Search Help page so that all features of the search are discoverable. Currently the only way to find out about this new feature is this forum post

Thanks for the quick update though!