But I have had a couple times where after my polite response, I didn't take it further, and was sent some pretty nasty messages.
In my opinion, no matter what you do, some people are going to complain. You didn't respond? Rude. You did respond but weren't really interested? Why are you wasting my time / leading me on? You responded, but not enough times or not quickly enough? etc etc
I take the approach of assuming I won't get a response to my messages, and send them out to people I find interesting. When I do get a response it's a pleasant surprise every time, as I have a new person I can get to know, and maybe establish a connection with. In a sense I think I prefer just not getting a response, because I don't need any excuses or to be told someone isn't interested in me. I know who I am, and am proud of that. If someone doesn't respond, that's their choice and as I said earlier, it's easier to assume they're not interested. I'm not saying this works for everyone, or feels great by any means, but there doesn't seem to be an established online etiquette and even Catholic Match a while ago had a blog post about that exact thing and how online dating sites are still relatively new, so firm rules on how to deal with messages and such aren't firmly established.
Just keep your head held high, be proud of who you are, and do your best. God willing, you'll find the right person, either through here or in real life. Either way though, I'll pray for your success.
I actually don't find that to be true-- no one has ever been able to answer the question of how long does one wait for someone to respond. A person might not log on regularly. She may not have received the e-mail notification. She may be on vacation, on a sequestered jury, a cruise, on military reserve duty, in jail, or otherwise not in a position to respond. Her phone might be broken (my colleague has probably gone through a dozen phones in the last few years) and she doesn't have a desktop or laptop computer. When you don't get a response, you are left to wonder and try to muster some Christian charity to excuse her non-response. When you get a response right away, even a negative response, then you can "quickly" move on to someone who is interested.