Praise be to Allah.
It is not permissible to use this app, because of what it leads to of mischief and negative consequences, including the following:
What you have mentioned about it paving the way for haraam relationships. Thus men can write words of praise and flattery, and expressions of love and romance, to young women, and vice versa. Once an inclination becomes entrenched in the heart, it becomes possible for each person to reveal his identity. This is spreading immorality among the believers. Allah, may He be exalted, says (interpretation of the meaning):
“Indeed, those who like that immorality should be spread [or publicized] among those who have believed will have a painful punishment in this world and the Hereafter. And Allah knows and you do not know”
Conceit and self-admiration that will develop in a person when he is flattered and praised, and he will begin to long for that and expect it. This could lead to his doom, as al-Bukhaari (2662) and Muslim (3000) narrated that Abu Bakrah said: A man praised another man in the presence of the Prophet (blessings and peace of Allah be upon him) and he said: “Woe to you! You have caused your companion’s doom, you have caused your companion’s doom” – several times. Then he said: “If one of you must praise his brother, let him say: ‘I think that So and so seems to be such and such, and Allah knows best about him, and I do not confirm anyone’s good conduct before Allah,’ if he knows that about him.”
This evil consequence still happens, even if a person does not know the people who are praising him. It is sufficient evil that he sees this praise and other people see it, and thus he is filled with pride and self-admiration.
Some people only subscribe to this app in order to hear this praise and flattery, and fulfil their desire for that. Thus they increase in self-admiration and pride.
Self-admiration is a serious spiritual disease that could lead to doom.
Ibn Qudaamah (may Allah have mercy on him) said: You should understand that self-admiration leads to arrogance, because it is one of the causes thereof. Self-admiration leads to arrogance, and arrogance leads to a great deal of bad conduct and bad attitudes.
End quote from Mukhtasar Minhaaj al-Qaasideen (p. 234).
It opens the door to rudeness, foul talk and bullying, as it gives jealous and hateful people the opportunity to express what they harbour in their hearts, and to expose people and disclose their secrets. All of these are things that Islamic teachings seek to prevent and bar the means that lead to them.
Allah, may He be exalted, says (interpretation of the meaning):
“And speak to people good [words]”
“but do not transgress. Indeed. Allah does not like transgressors”
At-Tirmidhi (2002) narrated from Abu’d-Darda’ that the Prophet (blessings and peace of Allah be upon him) said: “Nothing will weigh more heavily in the balance of the believer on the Day of Resurrection than a good attitude and manners. Indeed Allah despises the foul-mouthed rude person.” Classed as saheeh by al-Albaani in Saheeh at-Tirmidhi.
Muslim (11) narrated from ‘Aa’ishah that the Messenger of Allah (blessings and peace of Allah be upon him) said: …”Indeed Allah does not love harshness and harsh words.”
The Prophet (blessings and peace of Allah be upon him) said: “O you who have paid lip service to Islam, but faith has not yet entered your hearts, do not offend the Muslims, do not shame them, and do not seek out their faults, for whoever seeks out the fault of his fellow Muslim, Allah will seek out his faults, and when Allah seeks out a person’s faults, He will expose him even if he is in the innermost part of his home.”
Narrated by at-Tirmidhi (2032) and Abu Dawood (4880).
This app allows every hateful person to express what is in his heart that could hurt others, whether it is true or false.
Think about it: if a man leaves his wife and marries another woman, then the divorced woman logs onto that app and publicizes his faults that no one knows, adding to that or subtracting from it whatever she wants; or the man who divorced her logs on and lists her faults, so that her new husband, or a suitor who wants to marry her, sees that – how much evil and mischief would result from that?
What could be said about this being an opportunity for a person to find out his faults and for others to advise him counts for nothing in contrast to all these evil consequences. Moreover, the one who wants advice should seek it from those who are qualified to give it. If righteous people see a fault or shortcoming in their brother, they advise him and point that out to him in private, without announcing it publicly; thus they do not offend him and do not upset him, and they do not spread mischief among the people, for when evil is spoken of a great deal and is broadcast widely, people no longer think of it as a serious matter.
What do you think, if ten righteous people subscribed to this app, then someone logged in and listed their faults and shortcomings, whether that was true or false, how much would that make people averse to righteous and good people, and make those faults appealing to others in a subtle way, and make people feel inclined towards that, because of its being spoken about so widely and being attributed to those who people look up to and take as examples.
The evil consequences make it essential to stop using this app.
With regard to a forbidden thing that could lead to evil consequences, what benefit could there be in trying it out? Guard your dignity and rise above such things, may Allah increase you in guidance and keenness.
And Allah knows best.