"You could do worse than [x]"

Solution 1:

This is an example of litotes, which is stating a positive through a negative. It just means that [X] is not bad, that there are many alternatives that are worse.

In the sentence you link to

If you are just interested in a simple command line processor which uses MSXML 6 then you could do worse than using a simple JScript application.

the person who responded is suggesting that using a simple JScript application is a good choice.

Solution 2:

My favorite term for this sort of left-handed compliment (technically called a litotes, as @Robusto pointed out) is "praising with faint damns", a humorous inversion of the better-known "damn with faint praise" (which is so old that Alexander Pope is said to have stolen it from Wycherley.)

Solution 3:

It's a indirect compliment. You can go check out this link => http://www.english-test.net/forum/ftopic24532.html for more explanations.