Reduce spacing between columns in table created with kable(, format = 'markdown')

A couple of the examples in ?kable contain a padding argument. Feeding it 0L gets you closer, but it turns out that this argument will take negative integers, so

kable(table1, format = 'markdown', padding=-1L)

will produce something closer to what your are looking for.

I think what you are looking for is actually kable(table, "latex", booktabs = T). Also, you can check out the kableExtra package which makes it easy to modify the kable outputs.