I found this topic extremely interesting. I’m just studying Swedish but here’s how I understand deponents. Please comment on my misunderstandings. Most verbs can be used in active and passive form. Some examples: 1) Active form: De köper hans böcker. A plain active expression; form and meaning are active. 2) Passive form: Hans böcker köps av dem. An expression in passive voice where the agent ‘av dem’ denotes the actor. 3) Active form: Man köper hans böcker. In active voice, but the actor is undefined. 4) Passive form: Hans böcker köps. A plain passive expression; form and meaning are passive. In addition to these there are also other possibilities to form a passive expression: with verbs 'bli' and 'vara' and with formal subject ‘det’. Furthermore, the question which ones or how all these possible expressions are used in real language is out of scope. The forms 'köper' and 'köps' above are both actually forms of the same verb: 'att köpa'. The conjugation with the active form is: köpa-köper-köpte-köpt. And with the passive form: köpas-köps-köptes-köpts. For deponent verbs there is only a passive form available. Examples: 1) Passive form: Jag trivs här. An expression in active voice and meaning even though the form is passive. 2) Passive form: Man trivs här. This is exactly as the previous but the actor is not defined. The conjugation for the verb ‘att trivas’ goes like: trivas-trivs-trivdes-trivts. For deponents verbs there is no active form whatsoever. A form like ‘triva’ does not exists in Swedish. For many deponent verbs there is not anything which might even look like an active form, but unfortunately for some there is. For example forms like 'hoppar' and 'hoppas' are forms of completely different verbs: 'att hoppa' (to jump) and 'att hoppas' (to hope). All deponent verbs can be found in dictionaries. Personally I don't take deponents as a grammar issue. It’s all about studying vocabulary. There just are some verbs which cannot be used in active form.

-s can be added to almost every verb to make it mediopassive. I can't actually think of any verb that is still clearly active-transitive (can take a distinct transitive object) after taking the -s suffix, so I probably wouldn't call them deponents. "rummet känns kallt" seems equally understandable as a plain passive; reciprocals as in "vi träffas" are rare outside of these 1st person exclamations.