First of all, the Wiki makes text examples of filtering and doesn't show the actual Web interface. Apart from that, I always used multiple keywords in the same filter line, with no separator, but that doesn't seem to work right now. Finally, I saw mentions of a "Preview" button that would show the effect of active filters on the RSS feed, but I can't find it anywhere in my Web interface. I am using version 0.7.16 and the "Plush - gold" interface, like I was before my break.
Here's a screenshot explaining what I mean with multiple keywords and showing the absence of a Preview button:

Can anyone enlighten me? Thanks in advance!
