Something is wrong.Here is a break down of what's available:
+ to require a term (which is the default, so not required unless doing something more complex than a basic search)
- to exclude a term
| meaning 'or' e.g. metal|wood
" quotes to allow phrase searching e.g. "metal pipe"
http://www.diynot.com/diy/search/4867391/?q=sievert&o=date gets 16 results
http://www.diynot.com/diy/search/4867422/?q=seivert&o=date gets 1 result
But trying sievert|seivert gets no results. Should be 17 of them Doesn't even show a "http://www.diynot.com/diy/search/.../?q=sievert|seivert&o=date url as having been constructed.