Given the direction which Wittgenstein turned thereafter, it might be good idea to simply first take the statement literally, and not ascribe interpretation (e.g. about reference to God) to it. Taken that way, it is simply a logical necessity, so it can be neither a practice, nor advice, good nor bad.
So then, how does it apply in context? If we look forward from the Tractatus to where he is going next, the period between the Tractatus and the Investigations where his lectures were developing the notion of the language-game, then logical discourse itself, as laid out in the Tractatus, is simply an example of a single clear game, if one from which numerous others inherit.
In that context, this tautology comes to reflect the respect for the boundaries between language games. Within a given game, there are things to which the rules simply don't apply. One can make those moves, but they are either pointless, or they are disguised trickery, and either way, they are not useful participation in the ongoing dialog.
In this way, I think Wittgenstein returned to his original position, when he claimed the Tractatus would be dedicated "To the glory of God", if that would not be instantly misunderstood. In that frame of mind, there is a reasonable place to discuss God, as long as one realizes the purpose of doing so, and does not use the power of that domain to corrupt other domains of discourse.
Not coincidentally, from certain interpretations, the word he uses in German for 'to keep silent', is not simply a reference to quiet. It is not 'be still', which is much more common, but 'come to a close' or 'restrain oneself'. It is also the more traditional German translation of 'tacere' as the fourth "power of the Sphinx" (To know, to will, to dare, and to be silent.) So there is an element of respecting power, and an accusation of aggression against those who fail to do so, built into the statement. (It is also a pun, as it is the last word and the word for the end of a musical piece.)
Looking forward to the theory of language games, this is fitting, because it acknowledges that purposely crossing clarifying boundaries and bringing over power acquired in a different domain, is a kind of warfare against the topic in the name of contribution.