It appears that if smart quotes (“”) are used in the title of a question, then searching for the quoted text that includes a colon in quotes in a search doesn't show the question. Noting that the title of this question contains
“test: text” and
“xtest xtext”, compare these two searches:
and these two searches:
Yet searching for just one of the words with and without quotes has these results:
Now, for the really nasty part, both smart and dumb quotes in titles are rendered as smart quotes. For instance, in the title text of this question
dumb quotes is in dumb quotes. However, when copying this text from the title, the rendered smart quotes are copied as smart quotes. This means that if you highlight and copy “dumb quotes” from the title and search for it, you get zero results:
If you copy text from a title and paste it into the search box and surround it by quotes, the question from which you copied the text might not be included in the search results!
It's dangerous to speculate about bugs in code that you can't see, but I wonder whether smart quotes are treated as delimiters or letters in title text (e.g., does the title of this question contain the word
“test, and when the keyword handling in the search interface takes place.
How I came across this
I ran into this while adjusting some titles to include verbatim error messages so that future users have a better chance of finding them (and to help with comments like "searching for this error message on Stack Overflow already brings up [lots of results]."). I tend to use smart quotes while I'm typing, and have just realized that this may be self-defeating in this case. The particular case that got me to this was a Scheme error, "application: not a procedure":
These won't work for much longer. Whether the search functionality should be more robust or not, I need to be able to find these questions, so I'm going to remove the smart quotes from their titles.