I ran Comodo's AV for about a year or two, just out of curiosity, and hated it. It would halt legitimate Window's processes, flag so many background services, and pester me endlessly during installs. If I shut off certain features of the AV to stop pestering me, it was useless. They may have come up some in quality the recent months, but I wouldn't expect them to be that much better than before. The last test results from independent labs I saw (late last year), Comodo was pretty poor of a performer (if they were even bothered to be tested). I'd shut off the AV, and either go with none or get a better one. Your pick, but Comodo's AV just isn't worth toying with.
And like I said, while I don't like AVast, it's definitely a huge improvement over Comodo. Using online scanning is a common practice for me, even when Webroot finds a file it doesn't like (using a modified .dll file), and typically it's relatively harmless... you just need to know your file source, how to spot a real threat, and use proper surfing habits. You can pretty much make yourself 90+% infection-proof with good browsing habits, if you care to do it. The other 10% I'd say is due to infected USB drives, borrowed external drives, CDs burned with a virus, non-malicious government spyware (well, non-malicious until a hacker learns how to deal with it)... those kinds of things.