Can we delete /storage/emulated/0/tencent/MicroMsg/03a...df5/sfs/avatar.block.00008? What does this file do? It's part of wechat but is it just a cache of avatars? It's 256mb.
According to the info provided by this thread on XDA, any data contained within tencent/MicroMsg and its subdirectories, does not consist of chat backups and/or relevant data.

Instead, the folder tree contains several large cache files (for avatars and chats), and media files (pictures, music, video) sent to you by other users. This theory has been supported by the fact that, backing up the tencent/MicroMsg folders, uninstalling WeChat, reinstalling it, and then restoring the backed up tree, does not restore neither your previous chats, nor your old session.

Still, the app does never accomplish any maintenance on its cache, so that's a duty that must be carried out by the end user, while WeChat contacts and chats are stored within internal sql databases on the /data partition.