You’ve probably read or are going to read my post about that on G+ ;) so here’s the feature request for this:
Dolphin’s search offers to search for file name only (which is the default) and by "content". This content however also includes metadata, which is confusing. One would expect "Content" only searches for actual file contents, such as words in a document.
There should be a third option "Metadata" (a less technical term needed, though) that explictly lets you find files by their tags and comment etc.

I initially suggested having an additional "All" button that searches through all the three sources (file name, metadata, content) but it is probably better to have the buttons be checkable individually, so you can more accurate define what to search for.

Reproducible: Always

Steps to Reproduce:
Hit Ctrl+F
Actual Results:  
You can determin whether you want to search for file name or for file content+metadata ("Content")

Expected Results:  
There are three buttons: File name, Metadata, Content which can be checked individually.