## 1 Introduction  
The ubiquity of the Internet and social media has enabled customers to engage more with companies and other customers online and has made it easier for customers to complain about service failures [1]. Thus, understanding how firms should best recover customers in online contexts has become an important topic for both researchers and practitioners [2; 3; 4]. Past studies in online recovery indicated that the recovery strategies in offline recovery, such as tangible recovery strategies (e.g., compensation, discounts) [5; 6] and intangible recovery strategies (e.g., apologies, empathy, politeness) [4], are likely to be highly applicable in online recovery [2; 7]. However, customer participation, which is an important and novel offline recovery strategy to enhance customers' perceived justice and post-recovery satisfaction, has largely been overlooked in the online recovery context [2]. Moreover, [PERSON] and [PERSON] [8] have concluded that the extent of customer participation is not an obviously black and white distinction but is more suited for measurement along a continuum of different behaviors; however, extant studies in service recovery have investigated the effectiveness of customer participation typically using a dichotomous (participation or not) or trichotomous (firm, joint and customer recovery) construct that reflect only the extent of the effect of customers' labor input on service performance. Such a construct does not clearly explain the different effects on service interaction of the different behaviors exhibited during customer participation [8; 9], and it creates room for potential errors in measuring reliability [10]. In particular, different participation behaviors characterize the different roles that customers take in service performance, e.g., substituting for service employees' work or undertaking the responsibilities that they should bear, and they indicate different participation purposes, e.g., for guaranteeing normal service production or service enhancement [11]. Thus, different types of customer participation may induce different effects on service outcome [11; 12]. Mental accounting provides an ideal lens for analyzing this inference because this theory describes how customers take resources that are categorized into different accounts and given different values [13]. Thus, here, we verify this inference based on mental accounting theory to explain whether different types of customer participation (i.e., physical, mental, and emotional participation) have different effects on perceived justice and post-recovery satisfaction. Additionally, the employee's emotional intelligence is highly related to the customer's evaluation of recovery performance [14], e.g., an employee's ability to provide an apology with sincerity and empathy is essential to achieving the customer's forgiveness [15] and a positive evaluation of customer participation [16]. However, there has been a lack of attention on how to promote this ability in employees [14]. In particular, unlike traditional human interaction, due to a lack of non-verbal communication and social contextual cues in the online environment, the employee's interpersonal and emotional stances cannot be fully expressed through text-based language during online interaction [17], resulting in a reduction in the perception of the employee's empathy and sincerity [3]. Thus, how to break through these constraints that text-based language imposes on expressers is an important problem that needs to be resolved. [PERSON] [18] has concluded that the widespread use of online language such as emojis has greatly relieved this problem in informal conversations because an emoj can give online messages a more emotive-phatic function. However, whether emojis can produce the same positive effect in formal conversations such as those involving online recovery is uncertain.