There is search in the topic.
In user settings go to default user settings section and there should be an option to turn it on.
Each user can also change that setting in his user settings (there is a section with search settings)
It's not ideal, as it doesn't highlight the searched word and just takes you to the post it was found.
And as PitaJ said - you can improve the search, but you need to change the search engine from standard db search - as it just can't do what you want it to.
There is a solr plugin and unfortunately unmaintained elasticsearch one (So it might not work anymore). But I think you need to install solr and elasticsearch first to actually provide them with their backend.
If there is some light search engine better than database internal search, perhaps making a plugin with it and installing it by default would be better. But I didn't really look into internal search engines so no idea if that's possible or a good idea for default install.
EDIT: after a quick google search I found lunr.js (and elasticlunr that is supposed to be just lunr with some more functions), and flexsearch as node-based alternatives to solr. No idea if they make sense for this application, but I might try looking into a plugin using one of them after I finish with some other projects (so probably a month from now or more).