One thing you may want to try, if you're not doing this already, is to remove the actual numbers on the axes when you xkcd-ify graphs. I think people see the numbers and think that the results are precise and removing numbers that mean very little can have a pretty big effect on people's perception of the precision of the results. I say this because your first example still has the numbers on the axis ticks.
I came here to say exactly this - the purposeful imprecision in plots doesn't come from squiggly lines (which I consider unprofessional in many contexts), it comes from the lack of axes numbers. That first xkcd plot is the worst possible combination of communicating false precision while looking silly.
Context is also important. Sometimes, your audience will want to know exact numbers and imprecise plots will look bad. Imprecise plots should only be used to explicitly show a trend, which your audience should be expecting. If this is the context, they'll understand and squiggly lines are unnecessary.
I disagree with this. It drove me nuts when my first-year economics professor had a perfect Excel graph containing two crossed straight lines to demonstrate supply and demand. None of it made sense to me until she showed me a graph from her third-year course with actual data in it. xkcd-style graphs would have helped me with my understanding, as would drawing them on the blackboard.
As a potential counterxample for when you might want to remove numbers, a couple weeks ago I was presenting a proposed analysis pipeline for some data, and what I'd expect the results to look like. The x-axis points were all fixed, and clearly tied in to numbers I had discussed previously, and the y axis had experimentally meaningful ticks at 0, 1/2, 1, and 2.
I was, in fact, told later that the xkcd style graph was extremely helpful in conveying that it was not a graph of real data yet.
And if the numbers still feel important, don't put more than one or two of them. Knowing that the axis goes from 0 to 10k is probably enough information for something deliberately imprecise.
