XEP-Remarks/XEP-xxxx: Message Reactions
From XMPP WIKI
XEP-xxxx: Message Reactions
Summary of the advantages (pros) and disadvantages of adding a fallback body to the reaction.
- Users of legacy clients still see the reaction, because to them the message will appear as "standard" message.
- the legacy body causes the message to become "important" (in the sense of Carbons and MAM) without a hint (this is also a con).
- Legacy Client unusable because of reaction spam in MUCs, real messages with content are buried under reactions
- People might refrain from using reactions, as they notice how they spam others legacy client, which could effectively harm adoption of the feature