Table 2.

Summary of participation styles including name, metrics, and inclusion criteria.

Name			Metrics	Inclusion criteria
Multidimensional
	Content based
		Influential user [23]	69 activity, network, and content features including influential responding replies	Machine learning classifier (relying initially on expert judgement to identify exemplars)
		Leader [22]	68 activity, network and content features	Machine learning classifier (relying initially on expert judgement to identify exemplars)
		Opinion leader [16]	Word vectors, degree	Latent semantic analysis and high degree
		Information providers [29]	Social support type	High information support
		Community builders [29]	Social support type	High companionship support
		Emotional support providers [29]	Social support type	High emotional support
		Information seekers [29]	Social support type	High information support seeking
		Emotional support seekers [29]	Social support type	High emotional support seeking
		Information enthusiasts [29]	Social support type	High information support seeking, high information support
		All-around contributors [29]	Social support type	No particular metric stands out
		Balanced source user [20]	Source of information	Cited information from a range of sources
		Social media fan [20]	Source of information	High social media
		Organization follower [20]	Source of information	High organizations
		Homepage promoter [20]	Source of information	High static informational websites
		Seeker of health care [20]	Source of information	High health practitioners
		User of uncommon sources [20]	Source of information	High uncommon sources
		Sophisticated contributor [20]	Word count, source of information	High word count, high academic references
	Network based
		Key player [15]	Degree (nonredundant)	Key Player 1.4 software
		Hub [14,17,28]	Out-degree, in-degree	Hyperlink-induced topic search algorithm
		Authority [14,17,28]	Out-degree, in-degree	Hyperlink-induced topic search algorithm
		Facilitator [17,28]	Out-degree, in-degree	Hyperlink-induced topic search algorithm
		Trusted user [14]	Out-degree, in-degree	PageRank algorithm
		Help-seeker [14]	Out-degree, in-degree	Low in-degree, high out-degree (within the scope of the edge between 2 users)
		Star [27]	Out-degree, in-degree	Top ranked individual (outlier)
		Prime givers [14,27]	Out-degree, in-degree	Very high out-degree, high in-degree
		Serious members [27]	Out-degree, in-degree	Moderate out-degree, moderate in-degree
		Moderate users [27]	Out-degree, in-degree	Low out-degree, low in-degree
		Takers [27]	Out-degree, in-degree	No out-degree, low in-degree
	Activity based
		Caretaker [19]	Time logged in, episodes, reading, posting, thread initiation	High time logged in, low episodes, high reading, low posting, low thread initiation
		Here for you [19]	Thread initiation, posting, forum	Low thread initiation, high posting in support forum
		Butterfly [19]	Time logged in, episodes, posting, forum	High time logged in, high episodes, high posting in support forum
		Crisis-oriented individual [19]	Posting, forum	High posting in support forum
		Discussant [19,20]	Thread initiation, posting, forum	High thread initiation, high posting in discussion forum
		Average user [20]	Thread initiation, posting, forum, topic, days active, word count, source of information	No particular metric stands out
		Highly active relational poster [20]	Posts per day, thread participation, thread initiation	High posts per day, high thread participation, low thread initiation
		Topic-focused responder [20]	Thread initiation, posting, topic, days active	Low thread initiation, low posts per day, high fraction of topic-related posts, low days active
		Topic-spammer [20]	Posting, days active, word count, topic, source of information	Low days active, high posting, low word count, high fraction of topic-related posts, low references
		Long-term high-activity users [25]	Days active, posting	High days active, high posting
		Short-term high-activity users [25]	Days active, posting	Low days active, high posting
		Short-term low-activity users [25]	Days active, posting	Low days active, low posting
		Long-term low-activity users [25]	Days active, posting	High days active, low posting
Unidimensional
	Activity based
		High-engaged user	Posting	>2 posts [12]; top 1% of users [2,3]; top 10 users [24]; >180 posts [18]; top 100 users [21]
			Reading	>5 posts [12]
			Time logged in	Top 33.3% of users [13]
			Thread initiation	Top 100 users [21]
			Thread participation	Top 100 users [21]
			Network based
			Friendship	Mutual friend nomination between 2 users and >4 interactions between them [15]
			In-degree	Top 10 users [24]; high in-degree [26]
			Out-degree	Top 10 users [24]; high out-degree [26]
		Moderate-engaged user	Posting	2-10 percentile (9%) of users [2,3]
			Time logged in	Middle 33.3% of users [13]
			Network based
			Friendship	Friend nomination of another user and >0 interactions with them [15]
		Low-engaged user	Posting	1-2 post [12,18]; bottom 90% of users [2,3]
			Reading	1-5 posts [12]
			Time logged in	Bottom 33.3% of registered users [13]
			Network based
			Friendship	Any interactions with another user [15]