![](https://ip.bitcointalk.org/?u=https%3A%2F%2Fwww.imageupload.co.uk%2Fimages%2F2018%2F03%2F21%2FScreenshot_20180321-221626.jpg&t=664&c=aP9srfr9-Pd0Aw)
As you can see there is a word
NEW and it indicates that they have a new post on the thread(if they have replies) or that thread was recently posted(w/o replies). As for search engine, I'll suggest that searching on specific Boards/Child boards gives you a definite results than searching on entire forum.
Sorry I'd used meta section as a screencap sample.