The summit meeting of Soviet Bloc leaders that ended yesterday in Moscow contained both good news and bad for Poland's troubled attempt to move toward a more pluralistic form of communism.

The good news is that the Polish Communist Party has been granted what amounts to a breathing space by the Kremlin to demonstrate that it can defuse the crisis. The immediate threat of a Soviet invasion has receded with the statment that the participants at the summit consider the Polish people capable of solving their own problems.

The bad news is that the entire Soviet Bloc has now clearly defined its vital stake in the outcome of events in Poland. That Poland's leaders were summoned to explain their handline of the crisis before an emergency Warsaw Pact summit illlustrates the seriousness with which developments here are being viewed in the rest of Eastern Europe.

For now, the position of Poland's Communist Party chief, Stanislaw Kania, appears to have been strengthened. But the vote of confidence from his Warsaw Pact colleagues is only a temporary reprieve, conditional on his ability to deliver. Now that the crisis has become internationalized, it is likely that the performance of the Polish leadership will be scrutinized even more closely in Moscow, East Berlin and Prague.

This implies that in the longer term Kania's freedom of action may well have become more limited. That may make finding a lasting solution to the crisis more difficult. The Polish leaders are coming up against an ever more acute dilemma: the kind of reforms necessary for stability to be restored in Poland are precluded for ideological or political reasons.

With hindsight, it appears that last week's speculation in Western capitals about an imminent Soviet invasion of Poland may have been exaggerated. It obscured a more real threat: that, given the constraints under which it is operating, the Polish Communist Party may prove unable to contain the tide of events.

The emergence of the leading independent labor union, Solidarity, out of the August strikes along the Baltic Coast released hopes that can be satisfied only by structural changes in the system. The last three months have shown that Solidarity cannot simply restrict itself to narrow trade union activities. With the Roman Catholic Church, it has become a focus of popular resistance to the way Poland has been governed for the last 35 years.

The threatened general strike in the Warsaw region late last month over the imprisonment of a Solidarity volunteer was an example of the ease with which passions can become aroused. The workers' outrage quickly grew into demands for a reduction in the power of the security services. This may have helped set in motion the events that led to the Communist Party's dramatic appeal to the nation for calm last Wednesday and finally the Moscow summit.

Solidarity leaders are attempting to calm emotions now and the wave of strikes has subsided. But other conflicts could arise. Even within the Communist Party demands are welling up from rank-and-file members for greater democracy and new elections to all leadership bodies.

A major Polish newspaper, the government-controlled Zycie Warszawy, appealed for unity and calm today and said that a "grand coalition" of free trade unionists, Communists and Catholics should work together in a new era of cooperation. "Either our homeland will blossom in talent, work, freedom and tolerance or it will be gripped by a frost in which all flowers will fade," the paper said.

The immediate result of the Moscow summit, and the diplomatic saber-rattling that preceded it, may be a toughening in the Polish government's attitude toward the opposition. Already there are signs of a much more aggressive propaganda line with allegations that some Solidarity leaders are instigating chaos.

A statement today by the ruling Politburo called for stronger measures against "antisocialist forces who sow anarchy and confusion in social and economic life and pose a counterrevolutionary threat." The Politburo also explicitly recognized the interests of other Warsaw Pact countries in the Polish developments, welcoming their "solidarity and support." The crisis, it said, had "a momentous importance for the strength and security of the socialist states and for the process of detente in Europe."

Solidarity leaders have made no public comment about the summit, but one official said privately, "We regard this as a warning to the Polish party that our allies are ready to intervene here as a last resort. This could make relations between us and the government more difficult. It will encourage the hard-line faction, the people who want to make trouble for us."