Your version of Canon 87 can be read as you have suggested: people in second marriages can be readmitted to communion after a period of penance and purification.But he who leaves the wife lawfully given him, and shall take another is guilty of adultery by the sentence of the Lord. And it has been decreed by our Fathers that they who are such must be “weepers” for a year, “hearers” for two years, “prostrators” for three years, and in the seventh year to stand with the faithful and thus be counted worthy of the Oblation - Canon LXXXVII Trullo
Your version however differs in a rather significant way from the ones I’ve seen which end this way: …in the seventh year to stand with the faithful and thus be counted worthy of the Oblation* [if with tears they do penance.] ***
Penance includes the intent not to continue the sin. Since, as Canon 87 specified, people in second marriages are guilty of adultery, penance would have to include the intent to stop committing adultery.
Canon 54 addresses invalid unions (to close relations) and specifies that people in these situations:…fall under the canon of seven years, provided they openly separate from this unlawful union.
That is no different than what was promulgated in Canon 87, and the same idea is contained in Canon 3: there is no return to communion with the church until the irregular situation is ended.but that they who are involved in this disorder of a second marriage, but before our decree have acknowledged what is fitting, and have cut off their sin, and have put far from them this strange and illegitimate connection, or they whose wives by second marriage are already dead, or who have turned to repentance of their own accord, having learned continence…
It is only after the irregularity of the marriage has been ended that the individual can ask pardon for his sins.
Ender